Impact of co-occurring psychiatric disorders on retention in a methadone maintenance program: an 18-month follow-up study.

We assess the influence of co-occurring psychiatric disorders on retention in 189 opioid dependent patients in a methadone maintenance treatment (MMT) and determine the incidence of psychiatric co-morbidity during an 18-month follow-up period. About 68.5 % were retained in the MMT. Neither co-occurring mental disorders (chi-square = 0.303, df = 1, p = 0.622) nor methadone doses [85 (88.9) vs. 79.2 (85) mg/day, p = 0.672] were related to retention. In the follow-up period 19 new diagnoses were made, mainly major depression and antisocial and borderline personality disorders. Co-occurring psychiatric disorders should be assessed during MMT follow-up.