Introduction
Schizophrenia is a severe chronic mental health disorder characterized by delusions, hallucinations, thought disorder, and loss of functioning. Although symptoms may be debilitating, schizophrenia symptoms are often managed with a biopsychosocial approach including antipsychotic medication and psychosocial interventions (Jauhar et al., Reference Jauhar, Johnstone and Mckenna2022). Quality of life is recognized as an important outcome of psychotic illness with much research dedicated to this area in the last few decades (Renwick et al., Reference Renwick, Drennan, Sheridan, Owens, Lyne, O’Donoghue, Kinsella, Turner, O’Callaghan and Clarke2017).
Schizophrenia is also associated with a reduced lifespan; studies show that on average, people with schizophrenia have a reduced life expectancy of approximately 14.5 years (95% Cl 11.2- 17.8) compared to the general population (Galletly, Reference Galletly2017). Much of this reduction in life expectancy can be accounted for by the cardiovascular disease risk associated with metabolic risk factors such as diabetes, obesity, hypercholesterolemia, and cigarette smoking (Gates et al., Reference Gates, Killackey, Phillips and Álvarez-Jiménez2015). Furthermore weight gain associated with schizophrenia can be influenced by several factors including antipsychotic medication (Allison et al., Reference Allison, Mentore, Heo, Chandler, Cappelleri, Infante and Weiden1999, Basson et al., Reference Basson, Kinon, Taylor, Szymanski, Gilmore and Tollefson2001), negative symptoms, increased consumption of calorie-dense foods, and increased genetic susceptibility (Gates et al., Reference Gates, Killackey, Phillips and Álvarez-Jiménez2015). All these physical health issues could contribute to a reduced quality of life in those with schizophrenia. Hence, it is plausible that targeting nutrition and diet could improve quality of life outcomes in people with schizophrenia; however, to our knowledge this has not been comprehensively reviewed.
This systematic review evaluates the current literature of the relationship between nutritional interventions and quality of life for patients with schizophrenia. The paper also discusses benefits of these interventions and highlights areas for improving further research. Prior to the review, we hypothesized that nutritional interventions can significantly improve quality of life in individuals with a diagnosis of schizophrenia.
Methods
Inclusion and exclusion criteria
The study population for included studies consisted of individuals with a diagnosis of schizophrenia-spectrum disorder, including schizophrenia, schizophreniform disorder, and schizoaffective disorder or a psychotic disorder. Studies that had multiple diagnoses, including bipolar disorder, were excluded from the review. All studies for inclusion needed to implement a dietary intervention, such as cooking classes, psychoeducation on diet, or make recommendations for dietary intake. The study design needed to include both a pre- and post-measure of the intervention, or a control group comparison. Studies that contained an exercise intervention in addition to a dietary intervention were also included in the review. Included studies needed to report an outcome relating to quality of life, which was inclusive of both subjective and objective quality of life measures. Only studies published in a peer-reviewed journal in the English language and using human participants were included. Studies that lacked a diet or nutritional intervention were excluded, as they were not relevant in evaluating our proposed hypothesis for this review. Studies that only included a nutritional supplement intervention, such as the intake of vitamins, were also excluded from the review.
Search strategy
Systematic database searches were performed to find relevant trials. Studies were gathered for review using key nutritional, anthropometric, and psychiatric terminology from inception of databases up to December 2023. This search strategy was conducted on Medline, EMBASE, APA PsychINFO, CINAHL, and the Cochrane Library. The search terms used for Medline are outlined in Table 1, with more detailed information in relation to the other searches outlined in Supplementary Table 1. Additional scholarly systematic reviews and meta-analyses were manually searched to identify further studies.
Data extraction
Following the search strategy, the screening of relevant research articles consisted of two phases: a) an initial screening of the articles’ titles and abstracts; b) a full-text review. (Fig. 1). Two reviewers working independently screened all titles and excluded duplications and studies not meeting inclusion criteria. The two reviewers then carried out an independent screen of the abstracts and made further exclusions. The results from the two reviewers were compared at a meeting inclusive of senior investigators. Discrepancies and disagreements were resolved through consensus discussion with the full research team.
Figure 1. Preferred Reporting Items for Systematic Reviews and Meta-Analyses {PRISMA) 2020 flow diagram for new systematic reviews which included searches of databases, registers and other sources (Page et al., Reference Page, Mckenzie, Bossuyt, Boutron, Hoffmann and Mulrow2021), for more information, visit: http://www.prisma-statement.org/.
Results
After removing duplicates, a total of 982 articles were screened and 21 articles were assessed for eligibility. Nine articles met the inclusion criteria and results were collated in a spreadsheet (Table 2). Supplementary Table 2 provides further information in relation to weight outcomes in the selected studies. As studies in this review used a wide variety of questionnaires to evaluate the quality of life, Supplementary Table 3 explains each survey used and details the specific parameters that were assessed.
Table 2. Gives a chronological list of all studies included in the review together with information on participants’ number, country of origin, measures, study design used for quality of life determination and interventions undertaken
Abbreviations: F=female, M=male, QoL=Quality of Life, QLS, WHO=World Health Organization, WHOQOL-BREF= World Health Organization Quality of Life scale Brief Version, RAND=36-Item Health Survey including physical functioning, bodily pain, role limitations due to physical health problems, role limitations due to personal or emotional problems, emotional well-being, social functioning, energy/fatigue, and general health perceptions, MANSA= Manchester Short Assessment of Quality of Life questionnaire, Q-LES-Q= Quality of Life Enjoyment and Satisfaction Questionnaire, EQ-5D-5L= comprises five dimensions: mobility, self-care, usual activities, pain/discomfort and anxiety/depression.
When testing the effectiveness of an intervention, a variety of studies implemented a group approach. Five studies, namely Attux (Attux et al., Reference Attux, Martini, Elkis, Tamai, Freirias, Camargo, Mateus, Mari, Reis and Bressan2013), Centorrino (Centorrino et al., Reference Centorrino, Wurtman, Duca, Fellman, Fogarty, Berry, Guay, Romeling, Kidwell, Cincotta and Baldessarini2006), Kwon (Kwon et al., Reference Kwon, Choi, Bahk, Yoon Kim, Huang Kim, Chul Shin, Park and Geun Oh2006), Melamed (Melamed et al., Reference Melamed, Stein-Reisner, Gelkopf, Levi, Sivan, Ilievici, Rosenberg, Weizman and Bleich2008) and Sameby (Sameby et al., Reference Sameby, Soderberg and Hedstrom2008), all include an evaluation of the effectiveness of group-based cognitive behavioral therapy focusing on nutritional education, identifying barriers to change and how to implement healthier choices into their routine. All these studies demonstrated a statistically significant improvement in weight or body mass index (BMI) with the intervention during the active study phase, however results for quality of life outcomes differed.
Attux et al., reported no significant difference in quality of life (measured using WHO-QOL) after three months when comparing a lifestyle wellness group with a control group (Attux et al., Reference Attux, Martini, Elkis, Tamai, Freirias, Camargo, Mateus, Mari, Reis and Bressan2013). Similarly, Centorrino e al. found that the intervention did not provide a significant improvement in the quality of life for patients as measured using the Quality-of-Life-Questionnaire (QLS), and of note, this study had no control group (Centorrino et al., Reference Centorrino, Wurtman, Duca, Fellman, Fogarty, Berry, Guay, Romeling, Kidwell, Cincotta and Baldessarini2006). Kwon et al., using the WHO-QOL-BREF to measure quality of life found no significant impact using the intervention for psychological well-being, social relationships and the environment domain, or improvement in the physical health score (Kwon et al., Reference Kwon, Choi, Bahk, Yoon Kim, Huang Kim, Chul Shin, Park and Geun Oh2006). The study by Sameby et al., reported an improved quality of life (measured using MANSA) in six of the seven participants (86%) with an average increase of 10.7 points (please see Supplementary Table 3 for details of the scale), however this paper had a small sample size with no control group and did not report significance testing in relation to quality of life outcomes (Sameby et al., Reference Sameby, Soderberg and Hedstrom2008).
The study by Melamed et al., implemented a nutritional education program for inpatients with schizophrenia, along with group based behavior therapy (Reference Melamed, Stein-Reisner, Gelkopf, Levi, Sivan, Ilievici, Rosenberg, Weizman and Bleich18). A significant improvement (p = 0.04) in quality of life (measured using Quality of Life Enjoyment and Satisfaction Questionnaire) was revealed in the study group (3.27 at baseline versus 3.62 at 3 months follow-up, please see Supplementary Table 3 for details of this scale) compared to the control group (3.4 at baseline versus 3.4 at three months follow-up (Reference Melamed, Stein-Reisner, Gelkopf, Levi, Sivan, Ilievici, Rosenberg, Weizman and Bleich18).
The majority of studies identified through this review implemented an in-person intervention where participants were required to attend at different intervals to meet with their group or individual care provider (Attux et al., Reference Attux, Martini, Elkis, Tamai, Freirias, Camargo, Mateus, Mari, Reis and Bressan2013, Centorrino et al., Reference Centorrino, Wurtman, Duca, Fellman, Fogarty, Berry, Guay, Romeling, Kidwell, Cincotta and Baldessarini2006, Reference Hjorth, Medici, Juel, Madsen, Vandborg and Munk-Jørgensen27, Holt et al., Reference Holt, Gossage-Worrall, Hind, Bradburn, McCrone and Morris2019, Jakobsen et al., Reference Jakobsen, Speyer, Nørgaard, Karlsen, Birk, Hjorthøj, Mors, Krogh, Gluud, Pisinger, Nordentoft and van Wouwe2017, Kwon et al., Reference Kwon, Choi, Bahk, Yoon Kim, Huang Kim, Chul Shin, Park and Geun Oh2006, Reference Melamed, Stein-Reisner, Gelkopf, Levi, Sivan, Ilievici, Rosenberg, Weizman and Bleich18, Sameby et al., Reference Sameby, Soderberg and Hedstrom2008). One study delivered nutritional education via telephone-based classes consisting of eight telephone-delivered sessions focusing on goal setting, motivational interviewing, and cognitive behavioral strategies (Baker et al., Reference Baker, Turner, Kelly, Spring, Callister, Collins, Woodcock, Kay-Lambkin, Devir and Lewin2014). A resource booklet was posted to participants to guide them through their twice-weekly session, which included information on diet, sedentary behavior, smoking and alcohol, and recommendations for behavior change. The quality of life score (measured using WHO-8 QoL scale, please see Supplementary Table 3 for details of the scale) improved significantly (p = 0.017) from 25.6 to 28.4 by the end of the 4-week trial, however there was no control group in this study limiting its interpretation. In addition to the improvement in quality of life, the daily fruit and vegetable consumption increased significantly together with a reduction in reported leisure screen time, reduction in number of cigarettes smoked per day and an increase in walking per day.
Two of the studies included in this review, Holt (Holt et al., Reference Holt, Gossage-Worrall, Hind, Bradburn, McCrone and Morris2019) and Jakobsen (Jakobsen et al., Reference Jakobsen, Speyer, Nørgaard, Karlsen, Birk, Hjorthøj, Mors, Krogh, Gluud, Pisinger, Nordentoft and van Wouwe2017) did not find a statistically significant difference in quality of life score, weight or BMI. Holt and colleagues tested a 12-month intervention consisting of four 2.5-hour weekly group behavioral therapy sessions, followed by 2-weekly maintenance contact and group sessions at four, seven, and 10 months (Holt et al., Reference Holt, Gossage-Worrall, Hind, Bradburn, McCrone and Morris2019). The study included patients with a BMI>25 and focused on food as well as psychological processes underlying weight management and the challenges of living with psychosis and its impact on eating and weight. The study found no significant difference in quality of life (measured using RAND SF-36 and EQ-5D-5L) between the intervention and control group. There was a small but non-significant improvement in quality of life for the intervention group during the first 3 months, but the results were not maintained after 12 months. The study conducted by Jakobsen et al., evaluated the CHANGE intervention, a multifactorial training course consisting of lifestyle coaching and individual care coordination (Jakobsen et al., Reference Jakobsen, Speyer, Nørgaard, Karlsen, Birk, Hjorthøj, Mors, Krogh, Gluud, Pisinger, Nordentoft and van Wouwe2017). They aimed to motivate and support participants in finding realistic and attractive options for daily-life physical activity, healthy dietary choices (involving purchasing of food and cooking sessions), and smoking cessation. Participants received a personal meeting once per week by either a home visit, phone calls, text messages, or emails. The CHANGE lifestyle coaching intervention lasted 12 months and had a two-year follow-up. There was no statistically significant difference found in any of the three groups on BMI (p = 0.077) or quality of life outcomes as measured using the MANSA (p = 0.60) (Jakobsen et al., Reference Jakobsen, Speyer, Nørgaard, Karlsen, Birk, Hjorthøj, Mors, Krogh, Gluud, Pisinger, Nordentoft and van Wouwe2017).
Hjorth and colleagues (Reference Hjorth, Medici, Juel, Madsen, Vandborg and Munk-Jørgensen27) implemented a combination of individual and group sessions focusing on physical health in combination with treatment as usual. They assessed how their intervention affected newly diagnosed patients compared to long-term patients with schizophrenia. The group sessions discussed topics such as physical health problems and how to improve physical health and risk factors for poor health in a variety of health conditions. Individual sessions focused on optimizing physical health by modifying diet and physical activity levels. The study found that the increase in quality of life (measured using WHOQoL-BREF 26) among newly diagnosed patients was statistically significant in the physiological domain (p = 0.03) of the questionnaire and was also significant in the quality of life total score (p = 0.05) (Reference Hjorth, Medici, Juel, Madsen, Vandborg and Munk-Jørgensen27). The quality of life score did not change among long-term patients in any of the questionnaire parameters including physical health, psychological health, social relationships, and environment.
Discussion
This study suggests a modest impact of nutritional interventions on quality of life in schizophrenia spectrum disorders in some of the studies, with no impact found in others. Among these studies, weight and BMI also improved significantly for some of the interventions. Of the nine studies that were included in this analysis, only two of the studies (Reference Hjorth, Medici, Juel, Madsen, Vandborg and Munk-Jørgensen27, Melamed et al., Reference Melamed, Stein-Reisner, Gelkopf, Levi, Sivan, Ilievici, Rosenberg, Weizman and Bleich2008) reported statistically significant improvement in overall quality of life between the intervention and control group. The studies by Baker et al., Reference Baker, Turner, Kelly, Spring, Callister, Collins, Woodcock, Kay-Lambkin, Devir and Lewin2014, Centorrino et al., Reference Centorrino, Wurtman, Duca, Fellman, Fogarty, Berry, Guay, Romeling, Kidwell, Cincotta and Baldessarini2006 and Sameby et al., Reference Sameby, Soderberg and Hedstrom2008 reported pre- and post- study findings, but these studies were limited by the lack of a control group. Eight of the studies additionally investigated change in weight and BMI as one of their outcomes, in which five studies (Attux et al., Reference Attux, Martini, Elkis, Tamai, Freirias, Camargo, Mateus, Mari, Reis and Bressan2013, Centorrino et al., Reference Centorrino, Wurtman, Duca, Fellman, Fogarty, Berry, Guay, Romeling, Kidwell, Cincotta and Baldessarini2006, Kwon et al., Reference Kwon, Choi, Bahk, Yoon Kim, Huang Kim, Chul Shin, Park and Geun Oh2006, Melamed et al., Reference Melamed, Stein-Reisner, Gelkopf, Levi, Sivan, Ilievici, Rosenberg, Weizman and Bleich2008, Sameby et al., Reference Sameby, Soderberg and Hedstrom2008) reported statistically significant improvements. Overall, the studies suggest that interventions studied to date have at most a weak impact on quality of life, although the physical health benefits of nutritional interventions may still play an important role in delivering care.
People with serious mental illness are more likely to engage in unhealthy lifestyle practices, such as poor nutrition. However, best-practice models exist that provide the knowledge and tools to assist people with serious mental illness in making informed decisions about healthier lifestyle behaviors, including addressing tobacco use and excess weight (World Health Organisation (WHO), 2018). A challenge is how to integrate these practices effectively into routine behavioral health care (Ganguli et al., Reference Ganguli, Vreeland and Newcomer2007, Vreeland et al., Reference Vreeland, Minsky, Menza, Rigassio Radler, Roemheld-Hamm and Stern2003,(Pye et al., Reference Pye, Bash, Joiner and Beenstock2022). We believe there is a potential for greater impact and better quality of life in patients with an early dietary intervention, and the necessity of a multidisciplinary team getting involved at the outset of patient treatment has been acknowledged (see for instance Teasdale et al., Reference Teasdale, Mörkl and Müller-Stierlin2020).
There were several limitations noted among the studies. Some of the studies had a small number of participants and a high patient dropout rate with poor compliance to the intervention. Larger studies from a wide variety of cohorts are needed to investigate this further and improve generalizability. Follow-up duration is a further limitation of the studies with very limited evidence related to the impact of nutrition and dietary interventions in the longer term. It is possible that intervention benefits are only short-term and further research is needed with longer-term follow up. To improve the quality of life for patients with schizophrenia it is important to consider methods, which deliver health improvements for the full duration of these conditions.
Another limitation in several of the studies was that the participants were selected based on their willingness and motivation to lose weight (Attux et al., Reference Attux, Martini, Elkis, Tamai, Freirias, Camargo, Mateus, Mari, Reis and Bressan2013, Baker et al., Reference Baker, Turner, Kelly, Spring, Callister, Collins, Woodcock, Kay-Lambkin, Devir and Lewin2014, Centorrino et al., Reference Centorrino, Wurtman, Duca, Fellman, Fogarty, Berry, Guay, Romeling, Kidwell, Cincotta and Baldessarini2006, Holt et al., Reference Holt, Gossage-Worrall, Hind, Bradburn, McCrone and Morris2019), which could have introduced bias to the studies as participants were already at the stage where they were ready to make changes. The studies fail to reflect how these interventions would affect individuals who are not at that stage of change yet or are experiencing significant mental health deterioration. Additionally, some studies provided participants with compensation prizes for their time, which could have introduced further bias (Baker et al., Reference Baker, Turner, Kelly, Spring, Callister, Collins, Woodcock, Kay-Lambkin, Devir and Lewin2014). It may be worth examining those without an exercise component separately, as exercise could be a confounder for the impact on quality of life. However, due to the inclusion of studies that reported on nutritional interventions together with a measure on Quality of life, the number of eligible studies was relatively small and we were unable to investigate studies without exercise interventions separately. Strengths of this study include the review of a wide variety of diet and nutritional programs; the studies also applied the different diet programs in both inpatient and outpatient settings.
Clinical implications
When considering implementing a diet management program, it is essential to ensure the intervention can be feasibly delivered for the majority of the population. We suggest that a program that provides participants with the tools to carry out these new nutritional measures at home and at a low cost is likely to be most beneficial. Implementing nutritious eating and weight management interventions during the first stages of antipsychotic medication could prevent weight gain during the most significant period (Cordes et al., Reference Cordes, Thünker, Regenbrecht, Zielasek, Correll, Schmidt-Kraepelin, Lange-Asschenfeldt, Agelink, Kahl, Gaebel, Klimke and Hauner2014, Teasdale et al., Reference Teasdale, Ward, Rosenbaum, Samaras and Stubbs2017, Teasdale et al., Reference Teasdale, Mörkl and Müller-Stierlin2020). This could have critical long-term effects, including weight reduction, reducing metabolic risk factors, and improving the quality of life in patients diagnosed with schizophrenia.
In conclusion, the review provides preliminary evidence that nutrition and dietary interventions may have a weak but positive impact on some aspects of quality of life in the short term. The review strongly highlights that currently it is still difficult to inform practice and further research is needed due to substantial limitations in current literature such as small sample sizes, short follow-up durations and the use of diverse quality of life measures (see Supplementary Table 3). Further research is needed to investigate the potential for nutritional interventions to impact on quality of life, as well as other physical health outcomes in schizophrenia spectrum disorders.
Supplementary material
The supplementary material for this article can be found at https://doi.org/10.1017/ipm.2025.3.
Financial support
This work did not receive any financial support.
Competing interests
The authors have no conflicts of interest to disclose.
Ethical standards
The authors assert that all procedures contributing to this work comply with the ethical standards of the relevant national and institutional committee on human experimentation with the Helsinki Declaration of 1975, as revised in 2008. The authors assert that this study did not require ethical approval.
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