Epidemiology

The occurrence of psychiatric comorbidities among drug users in Europe varies significantly, with reports showing a wide range prevalence rate due to several factors such as types of substances use, sample studied, definition of comorbidity, time window and geographical areas assessed (EUDA 2015). Comorbidity rates of SUD and OMDs range from 35 to 75% in people seeking treatment for substance use (EUDA 2015; Hunt et al. Reference Hunt, Large, Cleary, Lai and Saunders2018; Kidorf et al. Reference Kidorf, Solazzo, Yan and Brooner2018; Kingston et al. Reference Kingston, Marel and Mills2017). Literature suggests that DD is more frequent among men in mental health units (87.5% men vs. 12.5% women, p < 0.001) (Rodriguez-Jimenez et al. Reference Rodríguez-Jiménez, Aragüés, Jiménez-Arriero, Ponce, Muñoz, Bagney, Hoenicka and Palomo2008) but more prevalent among women in addiction treatment programs (Brady and Randall Reference Brady and Randall1999; Chiang et al. Reference Chiang, Chan, Chang, Sun, Chen and Chen2007; Landheim et al. Reference Landheim, Bakken and Vaglum2003; Pedraz et al. Reference Pedraz, Araos, Garcia-Marchena, Serrano, Romero-Sanchiz, Suárez, Castilla-Ortega, Mayoral-Cleries, Ruiz, Pastor, Barrios, Chowen, Argente, Torrens, de la Torre, RodrÃguez De Fonseca and Pavón2015). Being female is considered a risk factor for psychiatric comorbidity among drug users (Torrens et al. Reference Torrens, Gilchrist and Domingo-Salvany2011), with a higher prevalence of specific disorders. A longitudinal study with 564 participants who injected drugs (34% female) reported higher psychological distress among females compared to male drug users, although no significant differences remained after controlling for temporal factors (Scott et al. Reference Scott, Carrotte, Higgs, Cogger, Stoové, Aitken and Dietze2016). However, a more recent study found that 53% of women with SUD admitted to a general hospital and attended by a consultation liaison addiction service (CLAS) had positive screening for DD with depression (46%), panic (46%) and generalized anxiety (38%) (Ferrer-Farré et al. Reference Ferrer-Farré, Dinamarca, Mestre-Pintó, Fonseca and Torrens2021). Disaggregating data by sex, a study found those screening positive at baseline were more frequently women (30.0% vs. 17.0%, p-value < 0.001) (Puértolas-Gracia et al. Reference Puértolas-Gracia, Barbaglia, Gotsens, Parés-Badell, Brugal, Torrens, Treviño, Rodríguez-Díaz, Vázquez-Vázquez, Pascual, Coromina-Gimferrer, Jiménez-Dueñas, Oliva, González, Mestre and Bartroli2022).

Among studies conducted exclusively with women, a cross-sectional study of 226 female injecting drug users from 5 European countries found that 87% of women met criteria for at least one comorbid lifetime psychiatric disorder (Tirado-Muñoz et al. Reference Tirado-Muñoz, Gilchrist, Fischer, Taylor, Moskalewicz, Giammarchi and Torrens2018), with the most common being depression (76%), panic (54%) and Post Traumatic Stress Disorder (PTSD) (52%) (Tirado-Muñoz et al. Reference Tirado-Muñoz, Gilchrist, Fischer, Taylor, Moskalewicz, Giammarchi and Torrens2018). Likewise, a recent systematic review with meta-analysis aimed to estimate prevalence of mental disorders among people with opioid use disorder, found that depression, anxiety, and PTSD disorders were the most common disorders among women (Santo et al. Reference Santo, Campbell, Gisev, Martino-Burke, Wilson, Colledge-Frisby, Clark, Tran and Degenhardt2022). Similarly, a recent study of 805 participants of people who use drugs (18% women), found that high to severe levels of distress were common and more prevalent among women (55% vs 37%) (Minoyan et al. Reference Minoyan, Høj, Jutras-Aswad, Vlad, Martel-Laferrière, Sylvestre and Bruneau2021). Notably, there is a significant lack of data on women with DD, particularly regarding the prevalence and specific combinations of SUDs and psychiatric conditions.

Gender differences/environmental factors

Gender differences refer to the distinct roles, behaviours, and attributes that societies and cultures attribute to individuals based on their sex. These differences can influence various aspects of life, including health outcomes, access to resources, and personal behaviours. Research has shown that men and women may experience different patterns of addiction and recovery due to these sex and gender influences (Becker and Koob Reference Becker and Koob2016; Fonseca et al. Reference Fonseca, Robles-Martínez, Tirado-Muñoz, Alías-Ferri, Mestre-Pintó, Coratu and Torrens2021; Greenfield et al. Reference Greenfield, Back, Lawson and Brady2010).

Environmental factors both facilitate and impede individuals’ daily functioning, interacting with personal characteristics like gender to create distinct challenges and opportunities (Ait-Daoud et al. Reference Ait-Daoud, Blevins, Khanna, Sharma and Holstege2017; Erol and Karpyak Reference Erol and Karpyak2015), being women and LGBTQIA + individuals particularly vulnerable to these influences. Exposure to violence, socioeconomic instability, increased stigma, lack of social support, social penalties, caregiving responsibilities and barriers to healthcare access are among the most significant challenges women might face. Women with SUD are more likely to suffer physical or sexual abuse, gender-based violence and Intimate Partner Violence (IPV) (Gilchrist et al. Reference Gilchrist, Blázquez and Torrens2012; Tirado-Muñoz et al. Reference Tirado-Muñoz, Gilchrist, Fischer, Taylor, Moskalewicz, Giammarchi and Torrens2018). Female partners of male substance users frequently experience coerced initiation into substance use, forced engagement in high-risk behaviours, and pressured participation in sex work to acquire the substance more quickly and efficiently (Fonseca et al. Reference Fonseca, Robles-Martínez, Tirado-Muñoz, Alías-Ferri, Mestre-Pintó, Coratu and Torrens2021). Although IPV also occurs in LGBTQIA + relationships, with a similar and even higher prevalence than in heterosexual relationships (Stiles-Shields and Carroll Reference Stiles-Shields and Carroll2015), women are more likely to suffer sexual violence, severe physical violence or to be killed by their male partners. Among women who use drugs, the frequency of IPV victimization is consistently higher than among other groups of women (Daigre et al. Reference Daigre, Perea-Ortueta, Berenguer, Esculies, Sorribes-Puertas, Palma-Alvarez and Grau-López2019; El-Bassel et al. Reference El-Bassel, Gilbert, Schilling and Wada2000; Gilchrist et al. Reference Gilchrist, Blazquez and Torrens2011; Hegarty et al. Reference Hegarty, Gunn, Chondros and Small2004; Pallitto et al. Reference Pallitto, García‐Moreno, Jansen, Heise, Ellsberg and Watts2013; Wagner et al. Reference Wagner, Hudson, Latka, Strathdee, Thiede, Mackesy-Amiti and Garfein2009). Furthermore, women show higher rates of unemployment, more social exclusion, and greater difficulties in fulfilling family and work obligations (Brady and Randall Reference Brady and Randall1999; De Waal et al. Reference De Waal, Christ, Dekker, Kikkert, Lommerse, Van Den Brink and Goudriaan2018; Torrens et al. Reference Torrens, Orengo, Rodríguez De Fonseca, Almodóvar, Baquero and Benito2021), leading to financial instability and poverty and significantly limiting the access to healthcare services (Martínez Reference Martínez2010). Factors that could impact the access to and use of healthcare services include the interaction and influence of systemic barriers (from institutional and societal values), structural barriers (related to service availability and organization), and individual/personal factors/barriers. Economic factors are also significant, particularly in regions lacking universal healthcare (Carrillo et al. Reference Carrillo, Carrillo, Perez, Salas-Lopez, Natale-Pereira and Byron2011; Priester et al. Reference Priester, Browne, Iachini, Clone, DeHart and Seay2016).

Women with a DD also experience a double discrimination, being stigmatized for their substance use, which is often more socially condemned for women than for men, as well as for their mental disorders. This dual stigma can lead to feelings of shame, guilt, and isolation, reducing the likelihood of seeking help or staying in treatment (Calderón Calvo Reference Calderón Calvo2021). Perceived and experienced stigma related to substance use has also been found to be a major obstacle for women in seeking and accessing reproductive health services (McCartin et al. Reference McCartin, Cannon, Harfmann, Dalton, MacAfee and Kusunoki2022). Interestingly, societal expectations regarding women’s roles can exacerbate mental health and substance use issues. In Western societies, women may feel pressured to conform to traditional caregiving roles, leading to emotional distress and discouraging them from seeking necessary help (Delgado-Herrera et al. Reference Delgado-Herrera, Aceves-Gómez and Reyes-Aguilar2024; Hay et al. Reference Hay, McDougal, Percival, Henry, Klugman, Wurie and Rao Gupta2019). Moreover, women with DD often lack robust social and familial support systems, which are essential for recovery. Beyond that, substance-using mothers face elevated child custody loss risk due to socioeconomic disadvantages, early motherhood, legal issues, mental health disorders, adverse childhood experiences, and high-risk substance use patterns, with limited formal treatment, prenatal care, and social support exacerbating their vulnerability and emphasizing the critical need for targeted interventions to support at-risk mothers (Canfield et al. Reference Canfield, Radcliffe, Marlow, Boreham and Gilchrist2017). Multidisciplinary, culturally appropriate care models can improve outcomes by reducing inconsistencies in healthcare and child protection decisions (Adams et al. Reference Adams, Ginapp, Price, Qin, Madden, Yonkers and Meyer2021; Powell et al. Reference Powell, Pilkington, Varney, Havard, Lynch, Dobbins, Oei, Ahmed and Falster2024). While children often motivate mothers to stop using substances, they can also be a barrier to accessing treatment, highlighting the critical importance of treatment programs that allow mothers to recover without being separated from their children. In fact, evidence shows that integrating children into the treatment process enhances maternal engagement and supports recovery (Chou et al. Reference Chou, Cooper-Sadlo, Diamond, Muruthi and Beeler-Stinn2020).

Clinical features

The treatment of SUDs significantly represents a therapeutic challenge due to their high rate of comorbidity with other mental health conditions (Davidson and White Reference Davidson and White2007). Women tend to exhibit a higher prevalence of comorbid psychiatric disorders compared to men (Carrà et al. Reference Carrà, Scioli, Monti and Marinoni2006; Erol and Karpyak Reference Erol and Karpyak2015; Fonseca et al. Reference Fonseca, Robles-Martínez, Tirado-Muñoz, Alías-Ferri, Mestre-Pintó, Coratu and Torrens2021) while also the literature establishes the “telescoping” as a phenomenon characterized by a faster progression from substance use initiation to the development of the SUDs among women (Greenfield et al. Reference Greenfield, Back, Lawson and Brady2010). Depression emerges as one of the most prevalent comorbid conditions with SUDs (Compton et al. Reference Compton, Thomas, Stinson and Grant2007; Grant et al. Reference Grant, Stinson, Dawson, Chou, Dufour, Compton and Kaplan2004; Herrero et al. Reference Herrero, Domingo‐Salvany, Torrens and Brugal2008), with evidence indicating that females seeking substance misuse treatment demonstrate higher rates of depressive disorders than men (Greenfield et al. Reference Greenfield, Back, Lawson and Brady2010). In fact, prevalence rates of mood and anxiety disorders demonstrate significant gender disparities, with women exhibiting higher rates both in the general population and among those with SUDs (Greenfield et al. Reference Greenfield, Back, Lawson and Brady2010). The presence of depression or anxiety disorders together with SUDs is associated with an increased severity of both conditions (Fonseca et al. Reference Fonseca, Robles-Martínez, Tirado-Muñoz, Alías-Ferri, Mestre-Pintó, Coratu and Torrens2021; Ford et al. Reference Ford, Gelernter, DeVoe, Zhang, Weiss, Brady and Kranzler2009; Smith and Book Reference Smith and Book2008), elevated risk of suicide attempts (Agosti and Levin Reference Agosti and Levin2006; Torrens et al. Reference Torrens, Gilchrist and Domingo-Salvany2011), and higher relapse rates (Agosti and Levin Reference Agosti and Levin2006; Daigre et al. Reference Daigre, Perea-Ortueta, Berenguer, Esculies, Sorribes-Puertas, Palma-Alvarez and Grau-López2019). Furthermore, the severity of depressive episodes shows an inverse relationship with both treatment adherence (Gjestad et al. Reference Gjestad, Franck, Hagtvet and Haver2011) and therapeutic response outcomes (Merrill et al. Reference Merrill, Reid, Carey and Carey2014). Gender differences are also evident in the temporal sequence of disorder onset.

Post-traumatic stress disorders (PTSD) are also found to be a frequent cooccurring diagnosis in patients with SUD (Brady et al. Reference Brady, McCauley, Back and El-Guebaly2021; Jacobsen et al. Reference Jacobsen, Southwick and Kosten2001), especially among women in which the prevalence and severity of PTSD is two to three times higher than in men (Olff Reference Olff2017). Although there is not a general agreement on the explanatory theory of this comorbidity, evidence has consistently shown that SUD increases the severity of PTSD and worsens the course of SUD (i.e., involving an earlier onset, longer time of use, presence of poly-substance use, more comorbidities and relapses, increased craving levels (Renaud et al. Reference Renaud, Jakubiec, Swendsen and Fatseas2021) and worst prognosis (Brady et al. Reference Brady, McCauley, Back and El-Guebaly2021). Individuals presenting with this DD frequently report antecedents of recurrent childhood sexual and physical abuse experiences, with higher prevalence rates among women (Blanco et al. Reference Blanco, Sió, Hogg, Esteve, Radua, Solanes and Moreno-Alcázar2020; Evans et al. Reference Evans, Goff, Upchurch and Grella2020; Huang et al. Reference Huang, Schwandt, Ramchandani, George and Heilig2012). The elevated rates of PTSD amongst females with SUDs correlate significantly with exposure to IPV, including physical and sexual assault (Grundmann et al. Reference Grundmann, Lincoln, Lüdecke, Bong, Schulte, Verthein and Schäfer2018; Jacobsen et al. Reference Jacobsen, Southwick and Kosten2001; Tirado-Muñoz et al. Reference Tirado-Muñoz, Gilchrist, Fischer, Taylor, Moskalewicz, Giammarchi and Torrens2018). The association between IPV and mental health problems has been extensively reported (Mason and O’Rinn Reference Mason and O’Rinn2014; McPherson et al. Reference McPherson, Delva and Cranford2007). A study conducted among 226 Women Who Inject Drugs (WWID) across Europe found that 61% of women had an intimate partner, 87% of women met criteria for at least one comorbid lifetime psychiatric disorder and the 70% experienced IPV in the past year. The most common pattern of IPV was severe combined sexual and physical abuse (37.2%). Additionally, IPV among women with SUD doubles the risk of developing PTSD (OR 1.95) (Tirado-Muñoz et al. Reference Tirado-Muñoz, Gilchrist, Fischer, Taylor, Moskalewicz, Giammarchi and Torrens2018). Substance use, mental health issues, and IPV are closely linked and co-occur, as substance abuse can increase aggression, mental health disorders can arise from or contribute to violence (Devries et al. Reference Devries, Mak, Bacchus, Child, Falder, Petzold and Watts2013; Tirado-Muñoz et al. 2018), and victims may turn to substances as a coping mechanism. Recent research has identified a distinct dissociative subtype of PTSD amongst women with SUDs, characterized by more severe psychopathological manifestations of PTSD and deficits in emotional regulation that are inversely related to adherence to treatment (Gidzgier et al. Reference Gidzgier, Grundmann, Lotzin, Hiller, Schneider, Driessen and Schäfer2019; Killeen and Brewerton Reference Killeen and Brewerton2023). Complex PTSD diagnosis encompasses additional symptoms, including emotional regulation deficits, interpersonal difficulties, and negative self-concept (Gidzgier et al. Reference Gidzgier, Bari, López-Atanes, Lotzin, Grundmann, Hiller and Schäfer2023).

Research examining the relationship between personality disorders (PDs) and SUDs has found evidence of a relationship between SUD and borderline personality disorder (BPD) (Trull et al. Reference Trull, Freeman, Vebares, Choate, Helle and Wycoff2018), especially amongst women who shows greater rates of BPD (Holdcraft and Comtois Reference Holdcraft and Comtois2002). The significant risks associated with this DD includes elevated rates of suicide attempts and engagement in high-risk sexual behaviours. This combination has also a negative impact on health and social aspects such as loss of relationships, employment and income. The explanatory theories of such comorbidity suggest that emotional dysregulation as well as impulsivity may play a relevant role in the development of both disorders (Trull et al. Reference Trull, Freeman, Vebares, Choate, Helle and Wycoff2018).

Individuals in recovery from an SUD appear to be particularly vulnerable to symptoms of eating disorders; weight concerns, maladaptive eating behaviours (Hodgkins et al. Reference Hodgkins, Jacobs and Gold2003; Jackson and Grilo Reference Jackson and Grilo2002) and excessive weight gain (Cowan and Devine Reference Cowan and Devine2008). Eating disorders frequently co-occur with alcohol use disorder (AUD) (Gadalla and Piran Reference Gadalla and Piran2007; Hudson, et al. Reference Hudson, Hiripi, Pope and Kessler2007; Root et al. Reference Root, Pisetsky, Thornton, Lichtenstein, Pedersen and Bulik2010), especially in women (Gail Gilchrist et al. Reference Gilchrist, Gruer and Atkinson2007). Recent studies indicate shared genetic risk for AUD and eating disorders (Munn-Chernoff and Baker Reference Munn-Chernoff and Baker2016). Underlying factors to this comorbidity include impulsivity and trauma (Wolfe and Maisto Reference Wolfe and Maisto2000), emotional dysregulation, low self-esteem, and anxiety (Harrop and Marlatt Reference Harrop and Marlatt2010; Munn-Chernoff and Baker Reference Munn-Chernoff and Baker2016; Schulte et al. Reference Schulte, Grilo and Gearhardt2016). Women with a DD often struggle with low self-esteem, shaped by past traumatic experiences and high comorbidity, and impaired physical quality of life (Daigre et al. Reference Daigre, Grau-López, Rodríguez-Cintas, Ros-Cucurull, Sorribes-Puertas, Esculies and Roncero2017). Despite substantial empirical evidence demonstrating distinct gender-specific clinical presentations, contemporary research frequently lacks robust gender-stratified analyses, thereby neglecting a crucial dimension in understanding DD and therapeutic approaches.

Treatment

In Europe, treatment of DD is hampered by the separation of mental health and addiction networks, the lack of clear policies as well as the need for different therapeutic approaches (EUDA 2015; Novotná Reference Novotná2013). In addition, inadequate staff training reduces motivation and complicates coordination of services (Baldacchino et al. Reference Baldacchino, Greacen, Hodges, Charzynska, Sorsa, Saias, Clancy, Lack, Hyldager, Merinder, Meder, Henderson, Laijarvi and Baeck-Moller2011), making difficult to address both conditions simultaneously. Although specific dual pathology units have been recently developed and implemented in some territories for the treatment of people with DD, this approach is still uncommon. In some territories, there still exist two separate networks, the addiction network for the treatment of people with SUDs (i.e., outpatient addiction centres, detoxification units, therapeutic communities, etc.) and the mental health network for the treatment of mental disorders (i.e., community mental health care centres, day care centres, psychiatric units in general or psychiatric hospitals, etc.). Due to this fragmentation of networks, comorbidity has been treated, and in some territories is still being treated, through parallel or sequential care, which results in poorer adherence, higher dropouts and worse therapeutic outcomes for both disorders (EUDA 2015; Mangrum et al. Reference Mangrum, Spence and Lopez2006; Priester et al. Reference Priester, Browne, Iachini, Clone, DeHart and Seay2016; Roncero et al. Reference Roncero, Barral, Rodríguez-Cintas, Pérez-Pazos, Martinez-Luna, Casas, Torrens and Grau-López2016). The integrated treatment is the model that seems to show the greatest effectiveness (Benito et al. Reference Benito, Jiménez-Murcia, Tirado-Muñoz and Adan2026; Donald et al. Reference Donald, Dower and Kavanagh2005; Drake et al. Reference Drake, Mercer-McFadden, Mueser, McHugo and Bond1998; Spivak et al. Reference Spivak, Strain, Spivak, Cullen, Ruble, Parekh and Mojtabai2020; Torrens et al. 2012) although more evidence is still needed. Literature has consistently pointed out that the integrated model could reduce the presence of the revolving door syndrome/phenomenon and duplication of interventions, which leads to poorer adherence and higher social and health care costs (UNODC 2022). Although authors agree on addressing dual pathology through a multidisciplinary approach, there is still a lack of consensus on the most appropriate treatment setting as well as the best pharmacological and psychosocial strategies to be used (EUDA 2023). In fact, a recent review of 7 studies about interventions in a general practice setting that targeted patients with DD, found no significant differences in mental health or SUD outcomes when comparing several integrated treatment models with different approaches and organizational combinations (Tranberg et al. Reference Tranberg, Colnadar, Nielsen, Hjorthøj and Møller2024). Most articles and reviews addressing comorbidity management in patients with SUD have focused on evaluating the efficacy of pharmacological treatments and their efficacy and safety outcomes have been extensively described in numerous scientific articles (Cunill et al. Reference Cunill, Castells, González-Pinto, Arrojo, Bernardo, Sáiz and San2021; Green Reference Green2006; Kelly et al. Reference Kelly, Daley and Douaihy2012; Sáiz et al. Reference Sáiz, Flórez, Arrojo, Bernardo, González-Pinto, Goikolea, Zorrilla, Cunill, Castells, Becoña, López, Torrens, Fonseca, Tirado-Muñoz, Arranz, Garriga and San2021; Salloum and Brown Reference Salloum and Brown2017; Torrens et al. Reference Torrens, Tirado-Muñoz, Fonseca, Farré, Gonzalez-Pinto, Arrojo and San2021). Likewise, in a recent systematic review of 48 studies about the organization of community health services for the treatment of DD, the lack of specific training for staff, poor management of resources and greater personalization of care plans, with attention to psychosocial interventions, were identified as critical aspects (Fantuzzi and Mezzina Reference Fantuzzi and Mezzina2020). Interestingly, evidence shows that psychosocial interventions seem to be the most appropriate approaches to address the gender specific needs of current SUD interventions. Although several reviews have examined psychosocial intervention for people with DD (Horsfall et al. Reference Horsfall, Cleary, Hunt and Walter2009; Hunt et al. Reference Hunt, Siegfried, Morley, Sitharthan and Cleary2014; Hunt et al. Reference Hunt, Siegfried, Morley, Brooke-Sumner and Cleary2019; Pennay et al. Reference Pennay, Cameron, Reichert, Strickland, Lee, Hall and Lubman2011; Siddiqui et al. Reference Siddiqui, Mehta, Coles, Selby, Solmi and Castle2024), few studies have identified specific interventions for women or LGBTQIA + individuals. For example, trauma-focused approaches are increasingly recognized as best practice for supporting women with substance use problems and PTSD (Simpson et al. Reference Simpson, Goldberg, Louden, Blakey, Hawn, Lott and Kaysen2021), including pregnant substance-using women (Flannigan et al. Reference Flannigan, Murphy and Pei2023; Morton Ninomiya et al. Reference Morton Ninomiya, Almomani, Dunbar Winsor, Burns, Harding, Ropson, Chaves and Wolfson2023). Several integrated trauma-focused treatment approaches have been described, with the distinction between present (or non-trauma-focused) and past (trauma-focused) approaches. Among the most recognized interventions emerges the Seeking Safety (SS) intervention, a 25-session manualized intervention based on CBT that is flexible and can be delivered in individual or group format to maximize acceptability and client access (Najavits Reference Najavits2002), that has shown large effect sizes regarding the improvement of both PTSD and SUD outcomes (Simpson et al. Reference Simpson, Goldberg, Louden, Blakey, Hawn, Lott and Kaysen2021). Likewise, evidence of effective interventions for reducing IPV victimization remains limited, despite its high prevalence among women who use drugs and its association with poorer mental health. A meta-analysis assessing the effectiveness of advocacy and CBT interventions in reducing IPV among female victims has only identified one intervention for women with SUD (Tirado-Muñoz et al. 2014), which was tested in a pilot randomized controlled trial that measured the efficacy of a 12-session group intervention in reducing IPV victimization, SU and depressive symptoms. Initial positive effects were found, making these interventions a valuable option for women with DD who have experienced IPV (Tirado-Muñoz et al. 2015). Stronger social support and long-term network relationships have been associated with lower trauma symptoms among women with SUD exposed to violence, thereby indicating that treatment should prioritize the promotion of interpersonal relationships and social networks (Brown and Welc Reference Brown and Welc2025).

Other important factors to be taken into consideration for the treatment of DD in women, include the risk of human immunodeficiency virus (HIV) and hepatitis C Virus (HCV) transmission. A brief psychosocial intervention, developed to reduce sexual and injecting risk behaviours associated with HCV among WWID, showed promising results in decreasing risks associated with HCV and improving negative mood (Gilchrist et al. Reference Gilchrist, Tirado-Munoz, Taylor, Fischer, Moskalewicz, Köchl and Torrens2017). Furthermore, pregnancy in women with SUDs must be considered. Within this population, compassionate, individualized and trauma-informed care is recommended. Integrated approaches have been shown to improve maternal and child well-being, prenatal and postnatal support, and social connectedness, thereby strengthening women’s recovery and stability (Flannigan et al. Reference Flannigan, Murphy and Pei2023; Hubberstey et al. Reference Hubberstey, Rutman, Schmidt, Van Bibber and Poole2019; Tarasoff et al. Reference Tarasoff, Milligan, Le, Usher and Urbanoski2018).

Although previous studies suggest that psychosocial interventions should be initiated early during treatment and, ideally, should be high intensity for better results (Murthy and Chand Reference Murthy and Chand2012), no clear consensus exists. More recently, Hunt et al. (Reference Hunt, Siegfried, Morley, Brooke-Sumner and Cleary2019) in their review and meta-analyses (n = 41) of trials evaluating integrated models of care, non-integrated models of care, CBT, Contingency management, Motivational interviewing (MI), Skills training and CBT + MI (always vs standard care) did not find high quality evidence to support any of these treatments over standard care to reduce substance use or improve mental or global health in patients with DD (Hunt et al. Reference Hunt, Siegfried, Morley, Brooke-Sumner and Cleary2019).

Epidemiology, environmental factors, and therapeutic recommendations in the LGBTQIA + population

Recent evidence suggests that LGBTQIA + individuals should also be considered as an important population in the study of DD. LGBTQIA + individuals exhibit higher rates of substance use and SUDs and are more likely to enter treatment with more severe conditions, facing an increased risk of depression, anxiety, suicide (OR: 4.36 [95%CI: 3.32; 5.71) (Marchi et al. Reference Marchi, Arcolin, Fiore, Travascio, Uberti, Amaddeo, Converti, Fiorillo, Mirandola, Pinna, Ventriglio and Galeazzi2022), trauma and PTSD (OR: 2.20 [95% CI: 1.85; 2.60]) (Marchi et al. Reference Marchi, Travascio, Uberti, De Micheli, Grenzi, Arcolin, Pingani, Ferrari and Galeazzi2023), along with greater vulnerability to HIV and HCV, particularly in the context of Chemsex. Additionally, they tend to experience a higher prevalence of microaggressions compared to their cisgender and heterosexual peers as well as discrimination and harassment (Casey et al. Reference Casey, Reisner, Findling, Blendon, Benson, Sayde and Miller2019; Kidd et al. Reference Kidd, Levin, Dolezal, Hughes and Bockting2019; Pachankis et al. Reference Pachankis, Williams, Behari, Job, McConocha and Chaudoir2020; Phillips et al. Reference Phillips II, Felt, McCuskey, Marro, Broschart, Newcomb and Whitton2020; Xin et al. Reference Xin, Schwarting, Wasef and Davis2023). Environmental factors such as early onset of substance use and negative relations with substance-using peers increase the risk of SUD and relapse in LGBTQIA + individuals (Lukowski et al. Reference Lukowski, Young, Morris and Tinkelman2016). Furthermore, stigma against LGBTQIA + individual also leads to negative SUD treatment outcomes, such as self-stereotyping, delaying or avoiding care, early treatment dropout, and services tailored for heterosexual individuals that cannot respond to their specific needs. Factors such as stigmatization, discrimination, harassment, and internalized homophobia further contribute to their mental health burden and prevent them from accessing appropriate care (Kidd et al. Reference Kidd, Levin, Dolezal, Hughes and Bockting2019; Marchi et al. Reference Marchi, Travascio, Uberti, De Micheli, Quartaroli, Laquatra, Grenzi, Pingani, Ferrari, Fiorillo, Converti, Pinna, Amaddeo, Ventriglio, Mirandola and Galeazzi2024; Silveri et al. Reference Silveri, Schimmenti, Prina, Gios, Mirandola, Converti and Bragazzi2022).

Although LGBTQIA + individuals experience higher rates of mental health issues, such as anxiety, depression, and suicidal thoughts (Cochran et al. Reference Cochran, Mays, Alegria, Ortega and Takeuchi2007; Penn et al. Reference Penn, Brooke, Mosher, Gallagher, Brooks and Richey2013) that can hinder substance use recovery, no specific psychosocial interventions have been identified for the treatment of DD within this population. However, some recommendations include an holistic approach to physical, mental health and social needs in order to prioritize overall well-being; use of inclusive and culturally appropriate language, especially in reference to trans and gender diverse people in order to validate and respect each person’s gender identity; positive communication to ensure safety, dignity and respect, and to promote affirmative therapy, thereby validating their identities and experiences (Coleman et al. Reference Coleman, Radix, Bouman, Brown, De Vries, Deutsch and Arcelus2022). In a study conducted with 274 sexual minority Australians, the use of affirming practices and inclusive language, increasing the knowledge about sexual minorities among professionals, the use of educational resources (i.e., cultural competency workshops, lived experiences), and seeking mentoring from service providers experienced in working with sexual minorities were reported as key factors (Bishop et al. Reference Bishop, Crisp, Grant and Scholz2022). One particular intervention called “TransAction” has been identified as a model programme for the decrease of HIV risk and risk behaviours, including number of sexual partners, substance use and sex work among transgender women with multiple vulnerabilities. However, this intervention is limited as DD was not included (Reback et al. Reference Reback, Clark and Fletcher2019). High quality research is needed to develop and assess the efficacy of psycho-social interventions that consider the specific needs of LGBTQIA + individuals.

Implementation of the sex-gender perspective on research studies on the field of addictions and DD

Research on addictions and DD have traditionally adopted a male-oriented approach. Incorporating sex-gender analysis into DD research can help to minimize bias, improve reproducibility and experimental efficiency, promote social equality in scientific findings and promote opportunities for discovery and innovation (Tannenbaum et al. Reference Tannenbaum, Ellis, Eyssel, Zou and Schiebinger2019). Furthermore, there is a positive correlation between innovation, competitiveness, and a country’s gender equality index (European Commission 2020). Nevertheless, deficiencies have been observed in publications, reports and research papers, starting with the gender of the researchers themselves, something known as gender gap.

Several studies highlight the disparity between men and women in authorship and the composition of research teams, with male figures prevailing in most healthcare fields (Lucas-Domínguez et al. Reference Lucas-Domínguez, Aragonés González, Sixto-Costoya, Ruiz-Martínez, Alonso-Arroyo and Valderrama-Zurián2024). They also point to the underrepresentation of women in leadership positions and speaker invitations compared to their male peers (Spector and Overholser Reference Spector and Overholser2019). The cross-cutting integration of sex and gender in the composition of the research team and in all phases of the research cycle (i.e., problem identification, study design and methods, analysis, reporting, and knowledge translation) is one of the priorities of the European Research Area (ERA) and the European Commission’s Gender Equity Strategy 2020–2025.

There is also a gender bias that arises during study design, leading to a lack of inclusion of sex-gender variables in the design, methodology and correct description of the sample under study (cells, tissues, animals, healthy volunteers or patients). As a consequence of this bias, the analysis and dissemination of results that can hardly be extrapolated inclusively to the entire population (Häusermann et al. Reference Häusermann, Kurer and Schwander2015; Gogos et al. Reference Gogos, Langmead, Sullivan and Lawrence2019; Lucas-Domínguez et al. Reference Lucas-Domínguez, Aragonés González, Sixto-Costoya, Ruiz-Martínez, Alonso-Arroyo and Valderrama-Zurián2024). Preclinic research has predominantly performed with only male subjects. Females have been systematically excluded as part of the sample in these studies due to the false belief that the estrous cycle introduces unacceptable variability. However, several studies refute this claim, even demonstrating that males exhibit greater within-group and between-subject variability in spontaneous behaviour than females (Levy et al. Reference Levy, Hunter, Lin, Robinson, Gillis, Conlin and Datta2023). Similarly, in humans, the variation in cognition, mental health, and physical health does not differ between men and women during reproductive age (Pritschet Reference Pritschet2022; Smarr et al. Reference Smarr, Ishami and Schirmer2021).

This gender gap persists in the health sciences and goes beyond addiction research, with inequalities evident in terms of participation and access, as well as a lack of sex-disaggregated data or a complete absence of a gender perspective (Sugimoto et al. Reference Sugimoto, Ahn, Smith, Macaluso and Larivière2019). Nonetheless, to comply with the guidelines for sex-gender inclusion and to avoid common statistical errors, some studies (Eliot et al. Reference Eliot, Beery, Jacobs, LeBlanc, Maney and McCarthy2023) address the following recommendations: (1) to ensure an equitable distribution of male and female participants in sample selection, aligning with the specific research question, except in cases where single-sex studies are scientifically warranted; (2) to incorporate sex-gender as an explicit variable within the statistical model to enhance the robustness of data analysis; (3) to present all relevant statistical outcomes related to sex-based comparisons, including main effects and interactions; (4) in exploratory studies with constrained statistical power, to transparently acknowledge methodological limitations while maintaining the highest standards of statistical rigor; and (5) regardless of the findings from sex-based analyses, to make disaggregated data by sex available for each sample, either within the main manuscript or as part of the supplementary materials, to promote transparency and reproducibility. Additionally, further training should be provided to biomedical researchers about practical sex-gendered analysis methods (Klinge Reference Klinge, Gibson and Galea2022), and funding initiatives should explicitly address how the challenges related to the gender perspective will be tackled at every stage of the study. Following these guidelines will help us reach significant achievements in research and policy in the field of addictions, thereby supporting the development of preclinical and clinical studies aimed at more accurately designing and evaluating sex- and gender-responsive treatments, interventions, programmes, and assessment tools in substance use disorders.

Finally, it is important to consider the inclusion of LGBTQIA + individuals in the research design and analysis when required, ensuring that these groups receive the appropriate support and interventions they need.

The current approach to the DD features an androcentric design in the interventions, available resources, and treatment services offered (Torrens et al. Reference Torrens, Tirado-Muñoz, Fonseca, Farré, Gonzalez-Pinto, Arrojo and San2021). Furthermore, in the field of substance use, women are frequently regarded as a “special population” within the realm of drugs (Mutatayi et al. Reference Mutatayi, Morton, Robles Soto, Pálsdóttir and Vale Pires2022). Consequently, studies on DD do not consider the role of the sex-gender approach in either their design or the analysis of their results. Given the lack of research and empirical data with a gender perspective in the field DD, there is a clear need to address this gap through the inclusion of a sex-gender perspective on research studies and interdisciplinary collaboration.