Significant outcomes
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Institutionalised minors show electroencephalogram immaturity, particularly increased slow-wave activity (e.g. theta), which has been linked to cognitive and executive dysfunctions.
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Early psychosocial deprivation impacts the development of brain regions associated with executive functions, increasing the risk of externalising psychopathological symptoms.
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Reducing the duration of institutionalisation and improving foster care quality are key factors in mitigating long-term cognitive and neuropsychological consequences.
Limitations
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The limited number of studies meeting the inclusion criteria restricts the generalisability of findings across different institutional settings.
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The predominance of cross-sectional designs hinders conclusions regarding the long-term effects of electroencephalogram (EEG) immaturity on cognitive development.
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The exclusion of doctoral and master’s theses, as well as studies using alternative EEG methodologies, may have led to the omission of valuable insights on the topic.
Introduction
The emphasis for neglected minors in residential care homes has traditionally been on basic care, often characterised by a high child-to-educator ratio, insufficient social and cognitive stimulation, and limited emotional support (Mason and Narad, Reference Mason and Narad2005; Nweze et al., Reference Nweze, Nwoke, Nwufo, Aniekwu and Lange2022). Currently, between 2.5 and 8 million minors find themselves in institutions worldwide, while 1.3 million live with foster families (Petrowski et al., Reference Petrowski, Cappa and Gross2017; Hillis et al., Reference Hillis, Unwin, Chen, Cluver, Sherr, Goldman, Ratmann, Donnelly, Bhatt, Villaveces, Butchart, Bachman, Rawlings, Green, Nelson and Flaxman2021; UNICEF, 2024). The absence of educational and therapeutic support, or inadequate support during institutionalisation, can have lasting, damaging effects on children’s neurocognitive development, especially when it occurs at a young age (Fox et al., Reference Fox, Levitt and Nelson2010). Children in residential care run a greater risk of suffering negative consequences in their emotional and psychological development compared to minors who are not institutionalised. The place and conditions of social coexistence play an important role in the minors’ maturation. Different studies indicate that the cognitive processes of minors in residential care are significantly lower than those of children who live with their families in a normative environment (Johnson et al., Reference Johnson, Guthrie, Smyke, Koga, Fox, Zeanah and Nelson2010; Lloyd and Barth, Reference Lloyd and Barth2011). Similarly, the minors’ development can deteriorate even further when such circumstances as abuse also occur at the same time (Herringa et al., Reference Herringa, Birn, Ruttle, Burghy, Stodola, Davidson and Essex2013), as happens with a high percentage of institutionalised children, who suffered abuse in their families or in their care homes (Bick and Nelson, Reference Bick and Nelson2016).
Various research studies point out that psychosocial deprivation in the context of residential care is related to disturbances in several cognitive processes, such as a reduced IQ in institutionalised minors (Van Ijzendoorn et al., Reference van IJzendoorn, Luijk and Juffer2008) or the lack of linguistic competence and accuracy in the use of semantics (Kumar et al., Reference Kumar, Behen, Singsoonsud, Veenstra, Wolfe-Christensen, Helder and Chugani2014; Chinn et al., Reference Chinn, Momotenko, Sukmanova, Ovchinnikova, Golovanova and Grigorenko2023). However, it is not only in the domains of intelligence and language where disorders can occur but also through a high prevalence towards psychopathological symptoms and disorders (Gunnar and Reid, Reference Gunnar and Reid2019). The most common problems are symptoms of internalising disorders, such as anxiety and depression, externalising disorders, and other problems related to the processing and expression of emotions (Humphreys et al., Reference Humphreys, Gleason, Drury, Miron, Nelson, Fox and Zeanah2015; Young et al., Reference Young, Luyster, Fox, Zeanah and Nelson2017), which tend to increase with age (Sonuga-Barke et al., Reference Sonuga-Barke, Kennedy, Kumsta, Knights, Golm, Rutter, Maughan, Schlotz and Kreppner2017). Nevertheless, some of the most consistent findings are the effects of institutional deprivation on the deterioration of attention abilities and executive functions in general (Pollak et al., Reference Pollak, Nelson, Schlaak, Roeber, Wewerka, Wiik, Frenn, Loman and Gunnar2010; McDermott et al., Reference McDermott, Troller-Renfree, Vanderwert, Nelson, Zeanah and Fox2013). It has also been connected to specific deficits in the executive functions, such as inhibitory control (McDermott et al., Reference McDermott, Westerlund, Zeanah, Nelson and Fox2012), response or error monitoring (Loman et al., Reference Loman, Johnson, Westerlund, Pollak, Nelson and Gunnar2013), and problems of attention (Espano, Reference Espano2013).
Over the last few decades, neuroimaging studies have been applied to the analysis of the general and specific neurological implications of the impact of institutional psychosocial deprivation (Sheridan et al., Reference Sheridan, Fox, Zeanah, McLaughlin and Nelson2012; Olson et al., Reference Olson, Heide, Alm and Vyas2015). At a structural level, it has been demonstrated that institutionalised children present lower total brain, grey, and white matter volumes compared to non-institutionalised minors, in addition to having a smaller head circumference (Hodel et al., Reference Hodel, Hunt, Cowell, Heuvel, Gunnar and Thomas2015; Sheridan et al., Reference Sheridan, Mukerji, Wade, Humphreys, Garrisi, Goel, Patel, Fox, Zeanah, Nelson and McLaughlin2022). Nevertheless, it is on a functional level that we find particularly relevant data for comparing basic and higher-order psychological processes (VanTieghem et al., Reference VanTieghem, Korom, Flannery, Choy, Caldera, Humphreys, Gabard-Durnam, Goff, Gee, Telzer, Shapiro, Louie, Fareri, Bolger and Tottenham2021). One of the techniques traditionally used to reflect the intrinsic dynamics of brain activity in repose is the electroencephalogram (EEG) (Anderson and Perone, Reference Anderson and Perone2018). This technique has been used as a biomarker of brain functioning in both cross-sectional studies (Vanderwert et al., Reference Vanderwert, Marshall, Nelson, Zeanah and Fox2010; Nagamitsu et al., Reference Nagamitsu, Yamashita, Ohya, Shibuya, Komatsu, Matsuoka, Ohzono and Matsuishi2011; Debnath et al., Reference Debnath, Tang, Zeanah, Nelson and Fox2020) and large-scale longitudinal studies (Norton et al., Reference Norton, MacNeill, Harriott, Allen, Krogh-Jespersen, Smyser, Rogers, Smyser, Luby and Wakschlag2021; Troller-Renfree et al., Reference Troller-Renfree, Costanzo, Duncan, Magnuson, Gennetian, Yoshikawa, Halpern-Meekin, Fox and Noble2022).
In typically developing children, resting-state brain activity shows a decline in the power of low-frequency bands, such as theta, alongside a progressive increase in higher-frequency bands, including alpha, beta, and gamma, from infancy through the age of eleven (Uhlhaas et al., Reference Uhlhaas, Roux, Rodriguez, Rotarska-Jagiela and Singer2010). This activity profile is also associated with specific skills. For instance, higher absolute power in the medium and high-frequency bands, such as alpha, beta, and gamma, has been associated with stronger language skills (Maguire and Schneider, Reference Maguire and Schneider2019), high cognitive skills (Williams et al., Reference Williams, Tarullo, Grieve, Wilpers, Vignola, Myers and Fifer2012), and good socio-emotional relationships (Brito et al., Reference Brito, Elliott, Isler, Rodriguez, Friedrich, Shuffrey and Fifer2019). The individual electroencephalographic differences found in institutionalised minors have been associated with distinct cognitive and behavioural outcomes. For example, the presence of greater absolute or relative low-frequency power (e.g. theta) has been linked to the development of behavioural, attention, and learning problems (Barry et al., Reference Barry, Clarke and Johnstone2003; McLaughlin et al., Reference McLaughlin, Fox, Zeanah and Nelson2011).
Although there have been many studies concerning the effects for minors suffering from neglect on a behavioural level, the effects on the underlying neuronal systems from behavioural and emotional deficits, as well as institutional psychosocial deprivation, have rarely been investigated. It is still unclear whether individual differences in resting brain activity are significantly related to long-term variations in cognitive processes. Thus, this review studies the EEG activity in institutionalised minors and its relation to psychopathological and neuropsychological symptoms, analysing the possible long-term consequences.
Method
This systematic review adhered to the PRISMA guidelines (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) (Page et al., Reference Page, McKenzie, Bossuyt, Boutron, Hoffmann, Mulrow, Shamseer, Tetzlaff, Akl, Brennan, Chou, Glanville, Grimshaw, Hróbjartsson, Lalu, Li, Loder, Mayo-Wilson, McDonald, McGuinness, Stewart, Thomas, Tricco, Welch, Whiting and Moher2021) and is detailed in Supplementary Materials, Table S1.
Selection criteria for articles
We used the following criteria to determine whether studies were eligible for inclusion: (1) scientific articles with quantitative data; (2) studies primarily aimed at observing the relationship between psychological and neuropsychological symptoms and the EEG spectrum in institutionalised children; (3) studies published in English between 2016 and 2023, as the last updated review on this topic was published at the end of 2015 (Perego et al., Reference Perego, Caputi and Ogliari2016); and (4) only studies in which the population consisted of children institutionalised in centres for minors or in foster care were considered, regardless of the presence of a control/comparison group. Studies where the population resided in residential health centres, intensive care units, operating rooms, or hospitals were excluded. Furthermore, studies were excluded if the sample consisted of children or adolescents with specific disorders or pathologies (e.g. intellectual disabilities and other neurodevelopmental disorders, cognitive impairments, autism, oncological conditions, traumatic brain injuries, sleep disorders, epilepsy, seizure disorders, and other neurological disorders, or alcohol abuse). Additionally, we excluded articles if the EEG measurements assessed cognitive processes outside the scope of this study. We also excluded reviews, doctoral theses, and undergraduate or master’s theses, focusing exclusively on peer-reviewed journal articles to ensure high methodological rigor and reliability. Finally, studies were excluded if the title, abstract, or keywords did not clearly indicate relevance to the research objective.
Search strategy and quality assessment
The search for articles to include in the review was carried out in the Web of Science, Scopus, PubMed, and Google Scholar databases in February 2024. The eligibility criteria were kept broad to encompass the range of empirical studies that met the inclusion criteria. The algorithm used for papers in each database was as follows: for example, Search ‘institutionalized care’ [OR] ‘residential care’ [OR] ‘foster care’ [AND] ‘child’ [OR] ‘child institutionalized’ [AND] ‘electroencephalogram’ [OR] ‘EEG’ [OR] ‘brain activity’ [AND] ‘psychopathology’ [OR] ‘externalizing problems’ [OR] ‘internalizing problems’ [AND] ‘Executive function’ [OR] ‘Executive functions’ [OR] ‘Executive functioning’ [OR] ‘EF’. The references of eligible studies and relevant reviews were also searched using a snowballing technique. The search yielded the following results across the databases: Web of Science, 524 articles; Scopus, 14; PubMed, 9; and Google Scholar, 1298.
During the selection process, two independent reviewers (N.B.I. and A.A.M.) performed quality assessments, identifying and removing duplicate articles due to repeated entries across different databases or languages. This resulted in a total of 66 articles, of which only 10 met the established inclusion criteria. To determine the suitability of these 10 articles for the review, their quality was assessed using the Newcastle–Ottawa Scale (Wells et al., Reference Wells, Shea, O’Connell, Peterson, Welch, Losos and Tugwell2000) and the adapted version for cross-sectional studies by Herzog et al. (Reference Herzog, Álvarez-Pasquin, Díaz, Barrio, Estrada and Gil2013) (Supplementary Materials Table S2). This scale provides a scoring system to compare studies based on factors such as study design, analysis, and presentation. To avoid the risk of biases, any disagreements between reviewers were discussed with J.M.M-M., resulting in a consensus on the selection of studies. The quality assessment process was overseen by C.B.-T. Once the quality check was completed, an exhaustive review of the selected articles was conducted to make a final selection decision.
This complex process of identification, search, and inclusion is clearly set out in the diagram in Fig. 1.
PRISMA flow diagram of systematic search and study selection according to Page et al. (Reference Page, McKenzie, Bossuyt, Boutron, Hoffmann, Mulrow, Shamseer, Tetzlaff, Akl, Brennan, Chou, Glanville, Grimshaw, Hróbjartsson, Lalu, Li, Loder, Mayo-Wilson, McDonald, McGuinness, Stewart, Thomas, Tricco, Welch, Whiting and Moher2021).
Data extraction and analysis
A piloted data extraction form was used to extract data from eligible articles, which were reviewed simultaneously and independently by two reviewers (J.M.M.M and N.B.I). Various data points were extracted from each of the articles: authors’ names, date of publication, the country where the research took place, objective of the study, number of participants including average age and gender of the sample, access to the sample, and the situation of the minors, as well as the instruments for evaluating and measuring brain activity, the conditions under which the measurements were made, and the results for each article.
Results
Following the inclusion criteria and after an exhaustive review, we only included and reviewed 10 articles.
Description of the results concerning the main data of the type of study of the articles reviewed
Regarding the objectives of the research work, the results show that all the articles investigate the relationship between psychopathological and/or neuropsychological variables in institutionalised minors. However, the study typology varies according to the nature of the sample. There are two clearly differentiated groups. First, those studies that conducted follow-ups of institutionalised minors through longitudinal designs, such as (1) Troller-Renfree et al. (Reference Troller-Renfree, Nelson, Zeanah and Fox2016), Wade et al. (Reference Wade, Fox, Zeanah and Nelson2019), Buzzell et al. (Reference Buzzell, Troller-Renfree, Wade, Debnath, Morales, Bowers, Zeanah, Nelson and Fox2020), Debnath et al. (Reference Debnath, Troller-Renfree, Zeanah, Nelson and Fox2023), Tan et al. (Reference Tan, Tang, Debnath, Humphreys, Zeanah, Nelson and Fox2023), and Wade et al. (Reference Wade, McLaughlin, Buzzell, Fox, Zeanah and Nelson2023). The samples in these studies were initially selected and evaluated in the Bucharest Early Intervention Project (BEIP) (see Zeanah et al., Reference Zeanah, Nelson, Fox, Smyke, Marshall, Parker and Koga2003) but followed completely independent objectives and subsequent evaluations. These studies included a control group of never-institutionalised minors (NIG) and consistently involved random assignment, which strengthened internal validity by assigning participants either to continued institutional care or foster care intervention groups (CAUG and FCG, respectively). Additionally, (2) the longitudinal study carried out by Bick et al. (Reference Bick, Lipschutz, Tabachnick, Biekman, Katz, Simons and Dozier2022) focused on a sample of internationally adopted children, without a non-adopted control group, thus limiting comparisons to within-group analyses. On the other hand, we have cross-sectional studies, which include (1) independent research conducted without a connection to any other study (An et al., Reference An, Zhukova, Ovchinnikova and Grigorenko2020), comparing adults with histories of institutionalisation (IC) to those raised in biological families (BFC) as a control group, without random assignment; (2) a cross-sectional study using a video game simultaneously with EEG recording (Hevia-Orozco et al., Reference Hevia-Orozco, Sanz-Martin, Guevara and Hernandez-Gonzalez2017), with EEG data later compared with standardised questionnaires (Hevia-Orozco and Sanz-Martin, Reference Hevia-Orozco and Sanz-Martin2018), using a control group of non-institutionalised adolescents, without random assignment; and (3) a cross-sectional study measuring mediofrontal theta power (MFTP) during a ‘go/no-go’ task with a sample from the BEIP study (Wade et al., Reference Wade, McLaughlin, Buzzell, Fox, Zeanah and Nelson2023), including a randomised control group of NIG. The studies demonstrate good methodological rigor, supporting the reliability of their findings on the relationships between psychopathological and neuropsychological variables in institutionalised minors.
In terms of effect sizes, all studies report not only statistical significance but also various effect size measures, such as η2, Cohen’s d, and standardised coefficients (β), to indicate the magnitude of observed effects. For example, studies like An et al. (Reference An, Zhukova, Ovchinnikova and Grigorenko2020) and Debnath et al. (Reference Debnath, Troller-Renfree, Zeanah, Nelson and Fox2023) provide effect sizes to quantify differences in neuropsychological outcomes, while others, such as Troller-Renfree et al. (Reference Troller-Renfree, Nelson, Zeanah and Fox2016); Buzzell et al. (Reference Buzzell, Troller-Renfree, Wade, Debnath, Morales, Bowers, Zeanah, Nelson and Fox2020); and Tan et al. (Reference Tan, Tang, Debnath, Humphreys, Zeanah, Nelson and Fox2023), use path analysis or regression models to capture the strength of associations between neuropsychological markers and psychopathological outcomes. This consistent reporting of effect sizes strengthens the interpretation of findings by highlighting the impact of institutionalisation on cognitive and emotional development.
Description of the results with respect to the instruments and recorded brain region
All the articles used instruments for neuropsychological and/or psychopathological evaluations, with the most common being the Flanker test (Troller-Renfree et al., Reference Troller-Renfree, Nelson, Zeanah and Fox2016; Debnath et al., Reference Debnath, Troller-Renfree, Zeanah, Nelson and Fox2023), the Health and Behaviour Questionnaire (HBQ) (Troller-Renfree et al., Reference Troller-Renfree, Nelson, Zeanah and Fox2016; Buzzell et al., Reference Buzzell, Troller-Renfree, Wade, Debnath, Morales, Bowers, Zeanah, Nelson and Fox2020; Debnath et al., Reference Debnath, Troller-Renfree, Zeanah, Nelson and Fox2023), and those used by Hevia-Orozco et al. (Reference Hevia-Orozco, Sanz-Martin, Guevara and Hernandez-Gonzalez2017) and Hevia-Orozco and Sanz-Martin (Reference Hevia-Orozco and Sanz-Martin2018).
Focusing on the analysed variables, we can see that there is variability in the characteristics, symptoms, or studied domains in each research study. A percentage of the studies focused on the cognitive and neuropsychological functions of institutionalised minors. The study carried out by Tan et al. (Reference Tan, Tang, Debnath, Humphreys, Zeanah, Nelson and Fox2023) focused on the mental subscale of the Bayley Scales of Infant Development (BSID-II), which measures cognitive skills including perceptual acuity, discriminations, memory, learning, communication, and abstract thinking skills, as well as intelligence quotient (IQ), assessing cognitive skills in four domains: perceptual reasoning, verbal comprehension, working memory, and processing speed in a situation of psychosocial deprivation experienced in institutions. An et al. (Reference An, Zhukova, Ovchinnikova and Grigorenko2020) evaluated the non-verbal intelligence and inhibitory control in aspects of early psychosocial deprivation produced in institutions. Wade et al., (2019, 2023) evaluated attention and short-term visual memory, spatial planning and problem solving, working memory and visual-spatial memory, and new learning in cases of early neglect in institutions; additionally, in Wade et al. (Reference Wade, McLaughlin, Buzzell, Fox, Zeanah and Nelson2023), they also analysed stressful life events.
Other studies focused on symptoms or psychopathological disorders. Troller-Renfree et al. (Reference Troller-Renfree, Nelson, Zeanah and Fox2016) and Debnath et al. (Reference Debnath, Troller-Renfree, Zeanah, Nelson and Fox2023) analysed internalising (depression, separation anxiety, and overanxious behaviour) and externalising (oppositional defiance, conduct problems, overt aggression, relational aggression, inattention, and impulsivity) behaviour, as well as the inhibition of responses on an executive functions level in environments of early psychosocial deprivation produced in institutions. Buzzell et al. (Reference Buzzell, Troller-Renfree, Wade, Debnath, Morales, Bowers, Zeanah, Nelson and Fox2020) assessed general psychopathology as did the previous studies, but employing a latent bifactor model in which a single factor captured the shared variance between domains of psychopathology (i.e. the ‘P factor’). Bick et al. (Reference Bick, Lipschutz, Tabachnick, Biekman, Katz, Simons and Dozier2022) also focused on children’s behavioural and emotional problems, in particular evaluating social competences, problems of internalising behaviour (anxiety, depression, somatic complaints and isolation), externalising behaviour (aggressive behaviour and criminal conduct) and a mixed factor (social problems, of both thought and attention) in early adverse environments produced in institutions. Finally, in the works of Hevia-Orozco et al. (Reference Hevia-Orozco, Sanz-Martin, Guevara and Hernandez-Gonzalez2017) and Hevia-Orozco and Sanz-Martin (Reference Hevia-Orozco and Sanz-Martin2018), they evaluated the internalising symptoms (anxiety, depression, and post-traumatic stress disorder) in institutionalised minors.
Another of the objectives of the article was to observe the relationship between the psychopathological and neuropsychological symptoms with the oscillations in the brain activity measured by an EEG. All the studies registered the general basal spectrum of the principal brain waves (delta, theta, alpha, beta, and gamma) (Tan et al., Reference Tan, Tang, Debnath, Humphreys, Zeanah, Nelson and Fox2023). However, for the analyses, some of them focused exclusively on theta (Debnath et al., Reference Debnath, Troller-Renfree, Zeanah, Nelson and Fox2023), alpha (Wade et al., Reference Wade, Fox, Zeanah and Nelson2019), carried out event-related potentials (ERPs) (Troller-Renfree et al., Reference Troller-Renfree, Nelson, Zeanah and Fox2016; An et al., Reference An, Zhukova, Ovchinnikova and Grigorenko2020), or registered MFTP while carrying out a go/no-go task (Buzzell et al., Reference Buzzell, Troller-Renfree, Wade, Debnath, Morales, Bowers, Zeanah, Nelson and Fox2020; Wade et al., Reference Wade, McLaughlin, Buzzell, Fox, Zeanah and Nelson2023). An increase in the slow waves (i.e. theta) was obtained as a result (Buzzell et al., Reference Buzzell, Troller-Renfree, Wade, Debnath, Morales, Bowers, Zeanah, Nelson and Fox2020; Bick et al., Reference Bick, Lipschutz, Tabachnick, Biekman, Katz, Simons and Dozier2022; Debnath et al., Reference Debnath, Troller-Renfree, Zeanah, Nelson and Fox2023; Tan et al., Reference Tan, Tang, Debnath, Humphreys, Zeanah, Nelson and Fox2023; Wade et al., Reference Wade, McLaughlin, Buzzell, Fox, Zeanah and Nelson2023), or a more immature EEG spectral power (Bick et al., Reference Bick, Lipschutz, Tabachnick, Biekman, Katz, Simons and Dozier2022) in the institutionalised minors who had experienced early psychosocial deprivation. These minors presented lower results in such domains as IQ (Tan et al., Reference Tan, Tang, Debnath, Humphreys, Zeanah, Nelson and Fox2023), attention (Wade et al., Reference Wade, Fox, Zeanah and Nelson2019; An et al., Reference An, Zhukova, Ovchinnikova and Grigorenko2020), visual memory, spatial planning, problem solving (Wade et al., 2019, 2023), and inhibition (Troller-Renfree et al., Reference Troller-Renfree, Nelson, Zeanah and Fox2016; Debnath et al., Reference Debnath, Troller-Renfree, Zeanah, Nelson and Fox2023), as well as a greater risk of experiencing externalising and internalising problems (Troller-Renfree et al., Reference Troller-Renfree, Nelson, Zeanah and Fox2016; Hevia-Orozco and Sanz-Martin, Reference Hevia-Orozco and Sanz-Martin2018; Bick et al., Reference Bick, Lipschutz, Tabachnick, Biekman, Katz, Simons and Dozier2022). Regarding decision-making, not all studies found difficulties in institutionalised minors (Hevia-Orozco et al., Reference Hevia-Orozco, Sanz-Martin, Guevara and Hernandez-Gonzalez2017).
Below is a description of the main data and results of each article (Tables 1 and 2).
Objectives of the research works, population, and evaluation instruments
Note: The ‘Study Quality’ category was assessed using the Newcastle–Ottawa Scale. BEIP, Bucharest Early Intervention Project; EF, executive functions.
Variables, instruments, and results of the articles
Note: NR, no response; DQ (Development Quotient[age equivalent score /- chronological age] × 100); ERN (error monitoring underlies a well-established ERP component known as error-related negativity (ERN), which is a negative deflection that is maximal at the frontocentral scalp sites and peaks within the first 100 ms following an error response); error monitoring works in tandem with inhibitory control by signalling and detecting errors in order to optimise behaviour goals (McDermott et al., Reference McDermott, Troller-Renfree, Vanderwert, Nelson, Zeanah and Fox2013; Moser et al., Reference Moser, Moran, Schroder, Donnellan and Yeung2013); EF, executive functions.
Discussion
The review provides a detailed description of the use of electroencephalographic techniques and psychological and/or neuropsychological tests as tools to gain greater knowledge of the functioning of the brains of institutionalised minors and to assist in the detection of the psychological and neuropsychological consequences present in these children. One of the main conclusions drawn from the review is that the psychological health of institutionalised minors is significantly impacted. As Gunnar et al. (Reference Gunnar, Morison, Chisholm and Schuder2001) point out, the heterogeneous and often co-existing aspects of deprivation can be understood on three levels: first, the lack of attention to basic needs, such as adequate health and nutrition; second, the lack of appropriate stimulation necessary for sensorimotor, cognitive, linguistic, and social development; and finally, the lack of stability and consistent relationships with significant adults, with whom to form emotional attachment. All these circumstances are reflected in the reviewed articles, in which the minors come from foster care (Troller-Renfree et al., Reference Troller-Renfree, Nelson, Zeanah and Fox2016; Wade et al., Reference Wade, Fox, Zeanah and Nelson2019; An et al., Reference An, Zhukova, Ovchinnikova and Grigorenko2020; Buzzell et al., Reference Buzzell, Troller-Renfree, Wade, Debnath, Morales, Bowers, Zeanah, Nelson and Fox2020; Bick et al., Reference Bick, Lipschutz, Tabachnick, Biekman, Katz, Simons and Dozier2022; Debnath et al., Reference Debnath, Troller-Renfree, Zeanah, Nelson and Fox2023; Tan et al., Reference Tan, Tang, Debnath, Humphreys, Zeanah, Nelson and Fox2023; Wade et al., Reference Wade, McLaughlin, Buzzell, Fox, Zeanah and Nelson2023) and even, in some cases, having been victims of abuse (Hevia-Orozco et al., Reference Hevia-Orozco, Sanz-Martin, Guevara and Hernandez-Gonzalez2017; Hevia-Orozco and Sanz-Martin, Reference Hevia-Orozco and Sanz-Martin2018). The background of physical, psychological, or sexual abuse suffered by these minors was probably greater than what is reflected in these studies, as pointed out by McDonald and Brook (Reference McDonald and Brook2009), who stated that 55% of those entering care centres had suffered child abuse or neglect.
One of the most relevant studies is the BEIP, begun in 2001 by Zeanah et al. (Reference Zeanah, Nelson, Fox, Smyke, Marshall, Parker and Koga2003). From this study arises part of the main sample used in the initial evaluations of several longitudinal studies included in this review (Troller-Renfree et al., Reference Troller-Renfree, Nelson, Zeanah and Fox2016; Wade et al., Reference Wade, Fox, Zeanah and Nelson2019; Buzzell et al., Reference Buzzell, Troller-Renfree, Wade, Debnath, Morales, Bowers, Zeanah, Nelson and Fox2020; Debnath et al., Reference Debnath, Troller-Renfree, Zeanah, Nelson and Fox2023; Tan et al., Reference Tan, Tang, Debnath, Humphreys, Zeanah, Nelson and Fox2023; Wade et al., Reference Wade, McLaughlin, Buzzell, Fox, Zeanah and Nelson2023). Although these studies share participants from the same original sample, each study pursued distinct objectives and conducted independent evaluations over the years. This study analysed the efficacy of foster care as an alternative to residential care. To do so, researchers included minors randomly assigned to foster homes, minors in residential care, and minors who were never institutionalised. The study lasted 54 months. However, as pointed out in our review, the minors were followed in a longitudinal manner, and the current research shows data from the evaluations of these groups at 12 and 16 years of age. During these years, many of the minors left institutional care for varying reasons. Nevertheless, throughout these decades, measurements were still being taken of behavioural, neuropsychological and psychopathological symptoms, as well as EEG. From this study (Zeanah et al., Reference Zeanah, Nelson, Fox, Smyke, Marshall, Parker and Koga2003), many later studies have arisen oriented towards studying a great number of variables, such as intelligence (Almas et al., Reference Almas, Degnan, Nelson, Zeanah and Fox2016), psychopathology (Humphreys et al., Reference Humphreys, Gleason, Drury, Miron, Nelson, Fox and Zeanah2015), cognitive skills (Humphreys et al., Reference Humphreys, King, Guyon-Harris, Sheridan, McLaughlin, Radulescu, Nelson, Fox and Zeanah2022), the neurobiology of the processing of emotions (Moulson et al., Reference Moulson, Fox, Zeanah and Nelson2009), alterations in the structure of the brain (Vanderwert et al., Reference Vanderwert, Marshall, Nelson, Zeanah and Fox2010), or electroencephalographic comparisons with other minors (Marshall et al., Reference Marshall and Fox2004). All of them include psychosocial deprivation occurring in institutions as a transversal theme; yet, in the review, we have focused solely on those studies with psychological and neuropsychological variables, as well as EEG measurements.
As for these variables, the minors who presented normative brain development were characterised by a decrease in the power of the lowest frequency EEG and an increase in the power of the highest frequency bands (Marshall et al., Reference Marshall, Bar-Haim and Fox2002; Anderson and Perone, Reference Anderson and Perone2018). Comparing these data with the results of the samples from our review shows that institutionalised minors have a general immaturity of the EEG, with slow waves predominating, principally in the theta band (Bick et al., Reference Bick, Lipschutz, Tabachnick, Biekman, Katz, Simons and Dozier2022; Debnath et al., Reference Debnath, Troller-Renfree, Zeanah, Nelson and Fox2023; Tan et al., Reference Tan, Tang, Debnath, Humphreys, Zeanah, Nelson and Fox2023), consistent with research into babies and children who have received institutional care (Vanderwert et al., Reference Vanderwert, Marshall, Nelson, Zeanah and Fox2010). This pattern is seen even in specific areas, such as the frontomedian (Buzzell et al., Reference Buzzell, Troller-Renfree, Wade, Debnath, Morales, Bowers, Zeanah, Nelson and Fox2020; Wade et al., Reference Wade, McLaughlin, Buzzell, Fox, Zeanah and Nelson2023), which is involved in inhibition, detection, and conflict resolution processes, as well as performance monitoring (Badgaiyan and Posner, Reference Badgaiyan and Posner1997; Fu et al., Reference Fu, Beam, Chung, Reed, Mamelak, Adolphs and Rutishauser2022). Furthermore, the results obtained with the ERN in institutionalised minors are consistent with studies showing that early exposure to prolonged adversity and neglect can lead to a lasting decrease in neuronal error processing (McDermott et al., Reference McDermott, Troller-Renfree, Vanderwert, Nelson, Zeanah and Fox2013; Frenkel et al., Reference Frenkel, Donzella, Frenn, Rousseau, Fox and Gunnar2020), even exhibiting a reduction in the ERN after possible adoption or fostering (Loman et al., Reference Loman, Johnson, Westerlund, Pollak, Nelson and Gunnar2013), or following child sexual abuse and/or neglect (Letkiewicz et al., Reference Letkiewicz, Spring, Li, Weinberg and Shankman2023). These findings may indicate continuous deficits in the development of brain circuits involved in error monitoring. Nevertheless, it cannot be concluded with any certainty that the early changes in brain activity can predict worse long-term cognitive results, despite the existence of data demonstrating that the changes in the EEG are related to certain cognitive dysfunctions (Troller-Renfree et al., Reference Troller-Renfree, Nelson, Zeanah and Fox2016; Hevia-Orozco et al., Reference Hevia-Orozco, Sanz-Martin, Guevara and Hernandez-Gonzalez2017; Hevia-Orozco and Sanz-Martin, Reference Hevia-Orozco and Sanz-Martin2018; An et al., Reference An, Zhukova, Ovchinnikova and Grigorenko2020; Buzzell et al., Reference Buzzell, Troller-Renfree, Wade, Debnath, Morales, Bowers, Zeanah, Nelson and Fox2020; Bick et al., Reference Bick, Lipschutz, Tabachnick, Biekman, Katz, Simons and Dozier2022; Debnath et al., Reference Debnath, Troller-Renfree, Zeanah, Nelson and Fox2023; Tan et al., Reference Tan, Tang, Debnath, Humphreys, Zeanah, Nelson and Fox2023). In order to determine how early brain activity is related to long-term cognitive development, it is important to examine the interaction between the cognitive and brain activity on multiple occasions, as done in the longitudinal studies carried out by the BEIP (Zeanah et al., Reference Zeanah, Nelson, Fox, Smyke, Marshall, Parker and Koga2003) and by Yarger et al. (Reference Yarger, Bernard, Caron, Wallin and Dozier2020), or to start new studies that include recent advances in the EEG, or to incorporate other neuroimaging techniques with spatial resolution in the initial stages of development (Hodel et al., Reference Hodel, Hunt, Cowell, Heuvel, Gunnar and Thomas2015).
As for the consequences or the impact of institutionalisation on the executive functions (Johnson et al., Reference Johnson, Policelli, Li, Dharamsi, Hu, Sheridan, McLaughlin and Wade2021), in the reviewed articles, the minors present worse results in working memory and processing speed (Debnath et al., Reference Debnath, Troller-Renfree, Zeanah, Nelson and Fox2023; Tan et al., Reference Tan, Tang, Debnath, Humphreys, Zeanah, Nelson and Fox2023), as well as in inhibition (An et al., Reference An, Zhukova, Ovchinnikova and Grigorenko2020). However, no significant problems were found in decision-making (Hevia-Orozco et al., Reference Hevia-Orozco, Sanz-Martin, Guevara and Hernandez-Gonzalez2017). One of the most relevant questions arising from this review is whether the executive functions could mediate between early psychosocial deprivation and psychopathology in institutionalised minors (Wade et al., Reference Wade, Fox, Zeanah and Nelson2019; Buzzell et al., Reference Buzzell, Troller-Renfree, Wade, Debnath, Morales, Bowers, Zeanah, Nelson and Fox2020). A possible explanation is that the frontoparietal network, which sustains the executive functions, is altered in many psychopathological disorders (Sha et al., Reference Sha, Wager, Mechelli and He2019), and children who have experienced early psychosocial deprivation show an altered function and structure in this very region (McLaughlin et al., Reference McLaughlin, Weissman and Bitrán2019). It can thus be concluded that inadequate environments over critical periods can fundamentally change the dynamics of the neurocognitive development (Nelson and Gabard-Durnam, Reference Nelson and Gabard-Durnam2020). Some research works have also demonstrated that institutionalised minors have a lower IQ in comparison to those minors who were in foster care, from early infancy to the age of 18 years (An et al., Reference An, Zhukova, Ovchinnikova and Grigorenko2020; Tan et al., Reference Tan, Tang, Debnath, Humphreys, Zeanah, Nelson and Fox2023). Removing a minor from institutional care may allow for recovery of IQ to normal ranges if they receive adequate stimulation (Nelson et al., Reference Nelson, Zeanah, Fox, Marshall, Smyke and Guthrie2007; Sonuga-Barke et al., Reference Sonuga-Barke, Kennedy, Kumsta, Knights, Golm, Rutter, Maughan, Schlotz and Kreppner2017). However, there are factors that could intervene in the said improvement in IQ, such as fostering at an early age and the quality of care the minor receives in the foster family (Nelson et al., Reference Nelson, Zeanah, Fox, Marshall, Smyke and Guthrie2007; Bos et al., Reference Bos, Fox, Zeanah and Nelson2009; Almas et al., Reference Almas, Degnan, Nelson, Zeanah and Fox2016; Wade et al., Reference Wade, Fox, Zeanah and Nelson2019; Humphreys et al., Reference Humphreys, King, Guyon-Harris, Sheridan, McLaughlin, Radulescu, Nelson, Fox and Zeanah2022).
Psychopathological symptoms can also be sensitive to institutionalisation. Institutionalised minors have a greater risk of suffering from psychopathological disorders and symptoms (McLaughlin et al., Reference McLaughlin, Fox, Zeanah, Sheridan, Marshall and Nelson2010; Hevia-Orozco and Sanz-Martin, Reference Hevia-Orozco and Sanz-Martin2018). The electroencephalographic power, through the relative and absolute power in the alpha, beta, and gamma bands indirectly explains the links between a longer time being institutionalised and a greater risk of externalising problems (Hevia-Orozco et al., Reference Hevia-Orozco, Sanz-Martin, Guevara and Hernandez-Gonzalez2017; Hevia-Orozco and Sanz-Martin, Reference Hevia-Orozco and Sanz-Martin2018; Wade et al., Reference Wade, Fox, Zeanah and Nelson2019), but not of internalising in infancy (McLaughlin et al., Reference McLaughlin, Fox, Zeanah, Sheridan, Marshall and Nelson2010; Bick et al., Reference Bick, Lipschutz, Tabachnick, Biekman, Katz, Simons and Dozier2022). This would suggest that early adversity in institutional care could intervene specifically in the neuronal systems involved in externalising problems related to disruptive behaviour, attention, and impulsiveness. These effects are consistent with other studies involving institutionalised children with the risk of externalising problems and the presence of attention deficit and hyperactivity disorders (McLaughlin et al., Reference McLaughlin, Fox, Zeanah, Sheridan, Marshall and Nelson2010), with a deficient interpersonal functioning (Almas et al., Reference Almas, Degnan, Radulescu, Nelson, Zeanah and Fox2012) as well as executive dysfunctions and bad behaviour regulation (Tarullo et al., Reference Tarullo, Garvin and Gunnar2011). Another finding linking psychopathology with EEG variations is that a reduction in MFTP reflects an indirect neuronal path connecting early institutional neglect with general psychopathology between 12 and 16 years of age and not solely with internalising or externalising problems. MFTP reduction is less pronounced in fostered minors than in those institutionalised. At the same time, the changes in the development of the theta mediofrontal predict greater reductions in the general psychopathology when care involves fostering (Buzzell et al., Reference Buzzell, Troller-Renfree, Wade, Debnath, Morales, Bowers, Zeanah, Nelson and Fox2020; Wade et al., Reference Wade, McLaughlin, Buzzell, Fox, Zeanah and Nelson2023).
In this review, we have verified that the duration of institutionalisation can be a key factor in cognitive development (Rutter and O’Connor, Reference Rutter and O.’Connor2004; Wade et al., Buzzell et al., Reference Wade, Fox, Zeanah and Nelson2019; Reference Buzzell, Troller-Renfree, Wade, Debnath, Morales, Bowers, Zeanah, Nelson and Fox2020). Prolonged institutionalisation is associated with reduced theta power, indicating general immaturity in brain development (Debnath et al., Reference Debnath, Troller-Renfree, Zeanah, Nelson and Fox2023). Moreover, other studies have found that children in residential care who were subsequently fostered can achieve functional levels similar to normotypical children, overcoming delays in cognitive and neurocognitive development (Colombo et al., Reference Colombo, de la Parra and López1992; O’Connor et al., Reference O’connor, Marvin, Rutter, Olrick and Britner2003). Compared to the review by Perego et al. (Reference Perego, Caputi and Ogliari2016), our review represents a 9-year update of scientific advances, incorporating more recent studies and more precise methodologies. First, we delve into the data collection methods, describing in detail the questionnaires used for psychological and neuropsychological assessment. Second, we focus on the techniques employed in EEG spectral analysis, including evoked potentials, MFTP, error-related negativity (ERN), and baseline activity. In addition, we provide a detailed description of the brain regions assessed and the types of waves recorded, providing a more specific analysis of the neurophysiological findings. Finally, unlike the previous review, our selection criteria clearly establish the need for included studies to jointly address psychopathology, neuropsychology, and EEG, ensuring a comprehensive approach to assessing the impact of institutionalisation on child development. Furthermore, the reviewed evidence indicates that early detection of EEG abnormalities in institutionalised children could help identify those at greater risk of developing neuropsychological and psychopathological difficulties, facilitating targeted interventions aimed at improving emotional regulation and executive functions (Marshall et al., Reference Marshall and Fox2004; Vanderwert et al., 2010, 2016; Law et al., Reference Law, Han, Lai, Lim, Ong, Ng, Gabard-Durnam, Wilkinson, Levin, Rifkin-Graboi, Daniel, Gluckman, Chong, Meaney and Nelson2023). Moreover, creating more stimulating environments and reducing the duration of institutionalisation could mitigate the negative effects observed in EEG, reinforcing the importance of foster care models and individualised care in child development (Vanderwert et al., Reference Vanderwert, Zeanah, Fox and Nelson2016; Wade et al., Reference Wade, Fox, Zeanah and Nelson2019; Debnath et al., Reference Debnath, Troller-Renfree, Zeanah, Nelson and Fox2023).
The information on the subject being dealt with in this review is novel but insufficient, as there are still only very few empirical studies that deal with such a complex subject. There are, therefore, more reasons to continue investigating in the future. It would also be a good idea to analyse the utility of other questionnaires, to attempt to replicate previous studies in order to be able to verify the results with larger samples, as pointed out by other authors (Tan et al., Reference Tan, Tang, Debnath, Humphreys, Zeanah, Nelson and Fox2023). Future research should prioritise longitudinal studies that analyse the evolution of EEG activity alterations and their impact on long-term neuropsychological symptoms. Specifically, it would be relevant to examine whether specific patterns, such as MFTP, impact the development of executive functions and whether impaired error monitoring remains a predictor of externalising problems in previously institutionalised adolescents (Troller-Renfree et al., Reference Troller-Renfree, Nelson, Zeanah and Fox2016). To overcome these limitations, it would be advisable to conduct repeated EEG measurements with cognitive control tasks, such as the Flanker Task, administered at different developmental stages (e.g. at ages 12 and 16) to assess changes in inhibition and cognitive control. Additionally, combining EEG with functional neuroimaging techniques would allow for a more precise analysis of the effects of institutionalisation on brain structure and function. Finally, expanding sample sizes could help improve our understanding of how institutionalisation affects brain development, cognitive performance, and mental health.
Finally, we should mention one of the possible limitations of our study: that doctoral and masters theses were not included (Oliveira, Reference Oliveira2016), as were other studies that, although they did not comply with the established inclusion criteria, could have been relevant, such as, for instance, those that did not take measurements of the basal activity of the EEG (Humphreys et al., Reference Humphreys, King, Guyon-Harris, Sheridan, McLaughlin, Radulescu, Nelson, Fox and Zeanah2022) or that only used measurements of the EEG (Vanderwert et al., Reference Vanderwert, Zeanah, Fox and Nelson2016; Debnath et al., Reference Debnath, Tang, Zeanah, Nelson and Fox2020; Sheridan et al., Reference Sheridan, Mukerji, Wade, Humphreys, Garrisi, Goel, Patel, Fox, Zeanah, Nelson and McLaughlin2022). Moreover, many of the studies included in this review are from specific samples, such as the BEIP, which may limit the generalisability of the results to other cultural and institutional contexts. Future research should be expanded to diverse populations to assess the broader applicability of these results. We could also have included some articles that studied other domains outside the objective of our study but that could also have been relevant, as is the case of the research carried out by Chinn et al. (Reference Chinn, Ovchinnikova, Sukmanova, Davydova and Grigorenko2021), who evaluated the development of the processing of emotions in prosody and the processing of prosody in speech, as well as Young et al. (Reference Young, Luyster, Fox, Zeanah and Nelson2017), who focused on the processing of facial emotions.
Conclusion
This review highlights the limited research on the impact of institutionalisation on brain activity and its relationship with psychopathological and neuropsychological symptoms. A total of 10 studies met the inclusion criteria, providing evidence that institutionalised minors exhibit altered EEG patterns, particularly an increase in slow-wave activity, which has been linked to cognitive impairments and a higher risk of externalising symptoms. The results of this study can be used to mitigate the negative effects identified in EEG activity at three different levels of prevention. First, preventing situations of child neglect (e.g. family adversity, substance use, etc.) that increase the likelihood of institutionalisation is crucial, given that prolonged institutionalisation has been associated with neurophysiological alterations, such as decreased activity in fast bands and increased activity in slow bands. Second, the early detection of neuropsychological and psychopathological deficits through systematic assessments allows for early intervention to minimise the impact of institutionalisation on the development of the nervous system (An et al., Reference An, Zhukova, Ovchinnikova and Grigorenko2020). Finally, developing interventions adapted to life in institutions, focused on stimulating affected cognitive functions and improving emotional regulation, may further reduce these negative outcomes. The available evidence suggests that foster care models and individualised care can act as resilience factors, reducing the adverse effects of institutionalisation on child development (Bick et al., Reference Bick, Lipschutz, Tabachnick, Biekman, Katz, Simons and Dozier2022; Wade et al., Reference Wade, McLaughlin, Buzzell, Fox, Zeanah and Nelson2023). These findings reinforce the need for child protection policies to integrate evidence-based approaches to improve the care and development of institutionalised children.
Supplementary material
The supplementary material for this article can be found at https://doi.org/10.1017/neu.2025.19
Data availability statement
No new data were created or analysed in this study.
Author contribution
Conceptualisation: C.B.-T., J.M.M.-M., N.B.-I.; methodology: C.B.-T., J.M.M.-M., A.A.-M.; writing – original draft: C.B.-T., A.A.-M.; writing – review and editing: C.B.-T., N.B.-I. All authors have read and approved the final version of the manuscript.
Financial support
This research received no external funding.
Competing interests
The authors declare no conflicts of interest.
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