Association between concurrent depression and anxiety and six-month outcome of addiction treatment.

Objectives: This six-month prospective study of 326 patients with substance use disorders assessed rates of depression and anxiety symptoms among patients entering addiction treatment and examined the effects of concurrent psychiatric symptoms on indicators of addiction treatment outcome.

Methods: Initial assessments included semistructured clinical interviews, the Addiction Severity Index (ASI), the Beck Depression Inventory (BDI), and the Symptom Checklist 90-Revised (SCL90-R). Patients were reassessed at six months to determine treatment outcome (abstinence status and duration of continuous abstinence).

Results: A majority of the sample (63 percent) had significant psychiatric symptoms at intake: 15 percent (N=49) presented with depressive symptoms, 16 percent (N=53) with anxiety symptoms, and 32 percent (N=105) with combined depressive and anxiety symptoms. Forty percent of patients who presented with combined depression and anxiety symptoms were abstinent at six months. These patients fared worse than those who were less symptomatic at intake, including those who presented with depression symptoms alone; in the latter group, 73 percent were abstinent at six months. The hierarchical regression models accounted for 22 percent of the variance in the duration of continuous abstinence, 26 percent of the variance in the frequency of drug use at six months, and 39 percent of the variance in abstinence status at six months. Key predictor variables included days in treatment, primary drug of abuse, frequency of drug use, and report of concurrent depression or anxiety symptoms at intake.

Conclusions: Concurrent depression or anxiety symptoms at intake had a small but significant predictive effect on addiction treatment outcome over and above factors that are clearly known to influence outcome (length of stay in treatment and initial addiction severity).