This study found evidence that psychosocial interventions primarily targeting heavy drinking among young people can improve symptoms of depression. This indicates that alcohol use interventions may be useful in reducing symptoms of depression as well as alcohol use in youth populations. However, this result should be interpreted with caution as the pooled effect estimate was relatively small (SMD = 0.26) and none of the included studies were judged to be at low risk of bias.
Comparison with other studies and possible mechanisms
The effect estimate found in the present study is lower than effect estimates found in a meta-analysis of psychotherapies targeting depression in adolescents (g= 0.55, 95% CI, [0.34-0.75]), and in young adults (g= 0.98, 95% CI, [0.79-1.16]); ). However, given the suboptimal quality and high heterogeneity of the included studies, the effect estimates of Cuijpers et al.  meta-analysis should be taken with caution. The effect estimate found in the present study is also lower than the effect estimates found for fluoxetine in young people (SMD = -0.51, 95% CI [− 0.99, − 0.03]). However, as the interventions included in this study did not directly target depression, a lower estimate of effect is not unexpected compared to interventions directly targeting depression.
The finding that interventions targeting alcohol consumption can improve depressive symptoms could be explained by several possible mechanisms, supported by research indicating that excessive alcohol consumption precedes more severe depressive symptoms. [14, 31]. First, evidence suggests that the metabolic, neurophysiological, and circadian rhythm changes that result from alcohol consumption increase the risk of depression. . Therefore, interventions targeting alcohol consumption may ameliorate depression through these biological mechanisms. Second, the hangover resulting from excessive alcohol consumption can contribute to a cycle of feeling unwell, tired, lack of concentration, guilt, anxiety, and low mood. , and therefore interventions that reduce excessive alcohol consumption could help break this cycle. Third, excessive alcohol consumption can lead to relationship difficulties, employment problems, lower grades, sexual and memory problems, as well as increase the risk of accidental injury. . Thus, it is possible that if relationships, work, studies, and other areas of life improve due to reduced alcohol consumption, symptoms of depression also improve. Fourth, a successful experience with reducing alcohol consumption could improve mood. Finally, it is also possible that some of these treatments have a direct effect on mood independent of any effect on alcohol consumption. Future research should examine potential mechanisms of change derived from the theory to improve our understanding of how interventions targeting heavy drinking in youth appear to improve depressed mood.
All of the studies eligible for inclusion in the meta-analysis involved participants of college age, which means that the results relate to a narrower age range than the WHO definition of a 10-year-old. at age 24 which was used in the research question of this study. In addition, all of the studies included in the meta-analysis were conducted in an academic setting, thus limiting their representativeness. Additionally, four of the five studies were conducted in the United States, and therefore the results may not be generalizable to other countries, including low- and middle-income countries. Additionally, the populations included tended to be largely white (although studies reported race/ethnicity inconsistently, and in one study not at all). A study  was with youth who identified as American Indian/Alaska Native, but data were not available for inclusion in the meta-analysis, despite attempts to contact the authors. Thus, more research is needed with young people from more diverse socioeconomic and cultural backgrounds.
Another limitation is that several intervention studies of young people with mixed substance use problems were identified, but did not report separate results for those who only used alcohol, meaning that these studies did not could not be included in the current review. Additionally, several adult studies were identified that included participants aged 18 to 24 years, but data for these people were not disaggregated from the full sample and therefore could not be included. Finally, none of the included studies were judged to be at low risk of bias. One of the main reasons for this was that the studies did not publish a predefined analysis plan. This is important to ensure that the results reported have not been selected from multiple analyses, and thus future research would benefit from the publication of a predefined analysis plan.
This review also has many strengths. Our searches were comprehensive, using broad search terms to maximize sensitivity, and reference lists of included studies were also checked. We screened over 6,000 records, and each record at the full-text screening stage was double-screened. All studies included in the meta-analysis assessed depression using well-validated scales, and the heterogeneity in the meta-analysis was 0%. Furthermore, although two studies included relatively short follow-up periods (one month), a sensitivity analysis indicated that the results still held when only studies with longer follow-up periods (12 and 16 months) were included. . Data (SMD and its variance) were calculated from studies that provided data that were not in a form that could be directly used in the meta-analysis according to the guidelines of the Cochrane Collaboration Handbook . When the authors did not provide enough data to allow these calculations, they were contacted directly to request these data.
Implications for practice
Excessive alcohol consumption among young people is a major public health problem in high-income countries. Since binge drinking in youth predicts a range of poor short- and long-term outcomes, and comorbid binge drinking and depression are associated with worse outcomes than either other problems alone (for example, lower overall functioning, life satisfaction, and increased risk of suicide; ), relatively brief interventions for binge drinking that also improve mood potentially offer significant benefits. Moreover, in light of growing evidence that a range of higher-order executive functions are still developing during adolescence and early adulthood , and that binge drinking during this period has negative psychological, neurological, physical, and social consequences, the current findings suggest that providing such interventions when binge drinking takes root is also likely to be helpful in treating mood problems. These findings also highlight the potential benefits of a more integrated approach to substance use and mental health, areas traditionally treated separately. .