Importance: Immigrants are at an increased risk for co-occurring mental health and substance misuse symptoms; however, effective treatments are lacking. Objective: To evaluate the effectiveness of the Integrated Intervention for Dual Problems and Early Action (IIDEA) program compared with enhanced usual care. Design, Setting, and Participants: This effectiveness randomized clinical trial was conducted from September 2, 2014, to February 2, 2017, in 17 clinics or emergency departments and 24 community sites in Boston, Massachusetts, as well as in Madrid and Barcelona, Spain. Equal randomization (1:1) in 2-person blocks was used, assigning participants to either the IIDEA treatment group (n = 172) or the enhanced usual care control group (n = 169). Intent-to-treat analyses assessed effectiveness, and post hoc analyses examined whether results varied by symptom severity or treatment dose. Eligible participants were between 18 and 70 years of age, self-identified as Latino, screened positive for co-occurring symptoms, and were not receiving specialty behavioral health services. Interventions: Participants were randomized to a 10-session IIDEA treatment or to enhanced usual care. Main Outcomes and Measures: Primary outcomes were changes in alcohol and drug misuse and results of a urine test for drug metabolites but not for alcohol misuse. Secondary outcomes were symptoms of depression, generalized anxiety, posttraumatic stress disorder, and overall mental health. Results: In total, 341 participants were randomized to either the IIDEA treatment group (n = 172; 94 [54.7%] female, mean [SD] age, 33.5 [11.6] years) or the enhanced usual care control group (n = 169; 80 [47.3%] female, mean [SD] age, 34.3 [11.8] years). No statistically significant effects of IIDEA were found for primary drug and alcohol outcomes (ASI Lite-drug score: β = -0.02 [SE, 0.69; P = .88; Cohen d, 0.00; 95% CI, -0.17 to 0.17]; ASI Lite-alcohol score: β = -0.01 [SE, 1.19; P = .66; Cohen d, 0.00; 95% CI, -0.12 to 0.12]; urine drug test result: β = -0.36 [SE, 0.43; P = .50; OR, 0.70; 95% CI, 0.30-1.61]), but statistically significant effects were observed for secondary mental health outcomes. The IIDEA treatment was effective in reducing depressive symptoms per the Public Health Questionnaire-9 score (β = -1.14; SE, 0.47; P = .02; Cohen d, 0.20 [95% CI, 0.04-0.36]), posttraumatic stress disorder symptoms per the Posttraumatic Stress Disorder Checklist-5 score (β = -3.23; SE, 1.59; P = .04; Cohen d, 0.25 [95% CI, 0.01-0.37]), and overall mental health symptoms per the Hopkins Symptom Checklist-20 (β = -0.20; SE, 0.07; P = .01; Cohen d, 0.25 [95% CI, 0.08-0.42]) and composite mental health (β = -3.70; SE, 1.75; P = .04; Cohen d, 0.19 [95% CI, 0.01-0.36]) scores at the 6-month follow-up. Exploratory analyses suggested that 6-month treatment effects occurred for patients whose drug misuse was moderate to severe at the baseline assessment. Among patients with moderate to severe substance misuse, IIDEA substantially reduced substance use per the urine test results (odds ratio, 0.25 [95% CI, 0.09-0.67]; P = .01). Treatment dose showed small to large effect sizes by outcome. Conclusions and Relevance: The IIDEA treatment did not change drug misuse but did improve secondary mental health and substance misuse outcomes for a heterogeneous population with moderate to severe symptoms; this finding provides a path for treating Latino immigrants with co-occurring mental health and substance misuse symptoms. Trial Registration: ClinicalTrials.gov Identifier: NCT02038855.
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