Adolescent treatment outcomes for comorbid depression and substance misuse: A systematic review and synthesis of the literature

Highlights

• CBT, MET, FCT and SSRIs treat adolescents with depression and substance misuse

• Treatments gains are inconsistent across measures of depression

• Treatment gains are equivocal for substance misuse

• Sequencing treatment to address substance misuse first might improve outcomes

• Improvements in reward processing and self-efficacy are two potential mediators

Abstract

The quantitative literature on the treatment of comorbid depression and substance misuse among adolescents was reviewed, including: (1) a synthesis of the empirical evidence of the multiple models of integrated treatment for depression and substance use, (2) an examination of proposed mechanisms underlying symptom change in these integrated treatment models targeting depression and substance use, and (3) a methodological critique and suggestions for future research. We reviewed 15 studies reporting on treatment outcomes among adolescents with comorbid depression and non-tobacco related substance use disorders (SUD) and general misuse. Although there is empirical evidence linking Cognitive-Behavioral Therapy (CBT), Motivational Enhancement Therapy (MET), and Family-Focused Therapy (FFT) to depression and SUD symptom reduction in adolescents, few studies have provided data on mechanisms that may account for this effect. Potential mechanisms include improvements in dysfunctional reward processing and self-efficacy. Although this review highlights promising findings for the treatment of comorbid depression and substance misuse in adolescents, further work is warranted; as such results could have important implications for intervention development.

Introduction

Depressive and substance use disorders (SUDs) are among the most prevalent mental health concerns of young people, and an estimated 18% of adolescents who report substance use have the comorbidity of depression (Armstrong and Costello, 2002). Such comorbidities can complicate the conceptualization and delivery of treatment. For example, co-occurring depressive and substance use disorders are associated with greater treatment attrition in adolescents (Kandel et al., 1999, Pirkola et al., 2011) when compared to rates for those presenting with either depression or substance use alone. Furthermore, adolescents with co-occurring problems also report smaller mental and physical health treatment gains after therapy (Baker et al., 2007, Davis et al., 2006, Hersh et al., 2014) and a poorer overall quality of life (Lubman et al., 2007). A research priority to aid treatment development for adolescents presenting with depression and substance misuse is to evaluate current treatment approaches for feasibility, efficacy and effectiveness, as well as to identify potential mechanisms that could be accounting for symptom reductions and improved functioning.

Current treatments for adolescent depression include behavioral therapy (Hetrick et al., 2015), Interpersonal Psychotherapy (IPT; Moreau et al., 1991), and Cognitive-Behavioral Therapy (CBT). More recently, computerized CBT interventions have been shown to have positive effects on symptoms of both anxiety and depression among youth (Pennant et al., 2015). Selective serotonin reuptake inhibitors (SSRIs), particularly fluoxetine, have a moderate effect on depressive symptomatology in adolescents (Usala et al., 2008). The efficacy of SSRIs can be improved by combining its use with CBT (March et al., 2007). Similarly, the most common psychosocial interventions for adolescents with SUDs include CBT, as well as, family therapy, 12-step programs and motivational interventions (Slesnick et al., 2008). The current review focuses on how therapies for depression and SUDs are integrated together to treat adolescents with comorbid depression and substance use or disorder.

In adults, there is evidence to support integrated treatment for comorbid depression and SUDs. For instance, in a meta-analytic review, integrated treatment was shown to have significant effects on the percent of abstinent days reported at post-treatment compared to single-focus treatment (e.g. treatment as usual and 12-step programs). There were, however, no changes in treatment retention rates nor was there a significant decrease in reported depressive symptomatology as a function of treatment type (Hesse, 2009). Often these integrated treatments include CBT, Motivational Enhancement Therapy (MET) and newer approaches, such as Acceptance and Commitment Therapy (ACT) are beginning to be tested (Richardson, 2013). Research into the pharmacological treatment of co-occurring depressive and substance use disorders suggests that medications for managing mood symptoms do not have a significant impact on substance use (Pettinati et al., 2013). While a consideration of adult findings is helpful, it remains unclear how such findings generalize to adolescent populations. Adolescents differ developmentally from adults in many ways, including their value of affiliation and autonomy (Ahammer and Baltes, 1972), as well as in their ability to process reward (Sturman and Moghaddam, 2012).

Currently, there exists reviews on the complexity of treating adolescents with comorbid depression and substance use (Hesse, 2009, Kaminer et al., 2007), the outcomes of concurrent treatment for adolescent depression and cannabis use (Kaminer et al., 2008), and adolescent SUD treatment with consideration for how depression affects treatment retention and outcomes (Hersh et al., 2014). However, no present review focuses exclusively on the quantitative literature on treatment outcomes for adolescent depression and all non-tobacco related substance use and disorder. Accordingly, this review sought to provide a focused synthesis and critique of the quantitative literature on adolescent treatment outcomes for comorbid depression and substance misuse. To achieve this aim, this paper (1) synthesizes the empirical evidence for the multiple models of integrated treatment for substance use and depression and (2) examines proposed mechanisms underlying symptom change in the integrated treatment of depression and substance use. Following the review, a methodological critique and guidance for future research are provided.