Depression, anxiety and comorbid substance use: association patterns in outpatient addictions treatment

Abstract

Depression and anxiety disorders commonly coexist with drug and alcohol use. Several general population surveys suggest non-linear associations between alcohol and depression symptoms. It is unclear whether such association patterns occur in clinical samples and in the context of poly-substance use. The aim of the study was to investigate the association patterns between substance use and common mental disorder (CMD) severity. Patients accessing a UK outpatient addictions service were recruited sequentially via routine treatment contacts. Psychiatric diagnosis and severity of symptoms were established using the revised clinical interview schedule (CIS-R) structured diagnostic interview; yielding WHO ICD-10 diagnoses for CMD. Data on substance use patterns in the last month and severity of dependence were collected using standardised measures. ANOVA and multivariate regression models were employed to investigate associations between CMD symptom severity and substance use patterns. The results of the multivariate regression analyses indicated a linear association between weekly alcohol use and CIS-R severity; this was statistically significant when adjusting for severity of dependence, poly-substance use, gender and age. Other drug use patterns were not directly associated with overall psychiatric symptom scores, but some evidence was found that specific patterns of drug use correlate with specific psychological symptoms. In conclusion, only alcohol use was significantly associated with psychiatric symptom severity in the context of poly-substance use. Contrary to epidemiological surveys in the general population, no evidence was found for non-linear associations between CMD and substance use in this clinical sample; nor did we find evidence that recent abstinence increases symptom severity.

Keywords:

• comorbidity
• depression
• anxiety
• drugs
• alcohol

Acknowledgements

The authors thank Veronica Dale who provided statistical advice. The CCAS research programme was supported by a grant from St. Anne's Community Services, a not-for-profit social care and mental health organisation based in Leeds, UK.