Background: The comorbidity of substance use, mood disorders, and anxiety has been proven in various studies, leading to many clinical implications. Objectives: This study aimed to evaluate the effectiveness of acceptance and commitment therapy (ACT) in depression and anxiety in individuals with substance use disorder. Methods: This quasi-experimental study utilized a pretest-posttest design with a control group. The statistical population consisted of all people with substance abuse in Urmia in 2019, including 220 subjects. The sample consisted of 50 individuals with substance use disorders selected by purposive sampling and randomly assigned to experimental and control groups. The experimental group was trained in eight sessions, each lasting 90 min, based on the ACT protocol by Hayes et al. (2004), while the control group did not receive any intervention. The data were obtained using the Beck Depression Inventory and Beck Anxiety Inventory. Pretest and posttest were performed in both groups. The collected data were analyzed by multivariate analysis of covariance (MANCOVA) using SPSS23 software. Results: The results showed that after controlling for the pretest effects, a significant difference was observed between the mean posttest scores of the two groups in both depression and anxiety (P < 0.05). Conclusions: Acceptance and commitment therapy is an appropriate strategy to effectively improve depression and anxiety in people with substance use disorder.
