Background. Increasing attention has been directed in recent years to the detection and treatment of psychiatric co-morbidity among depressed individuals. The overlap of social phobia (SP) and avoidant personality disorder (APD) has been well recognized and a relationship between these disorders and depression has been suggested.

Methods. The pattern and clinical implications of co-morbidity of SP and APD with major depressive disorder (MDD), diagnosed by DSM-III-R criteria, were studied among 243 out-patients presenting with depression.

Results. Overall, 26·7% of adults in our sample with MDD met criteria for SP and 28·4% for APD. Almost two-thirds of depressed adults meeting criteria for social phobia or avoidant personality disorder met criteria for both (SP+APD). Depressed adults who met criteria for both SP+APD exhibited a significantly higher proportion of atypical depression (54·8%) compared with those with neither SP nor APD (31·1%). Among depressed patients, the co-occurrence of SP with APD was also associated with an earlier age of onset of MDD, a greater number of co-morbid Axis I diagnoses, and greater impairment of social adjustment and assertiveness.

Conclusions. Results confirm the overlap of SP and APD in a depressed population and the high prevalence of these disorders in MDD. They suggest that depressed individuals with both SP and APD but not SP alone are at particularly high risk for atypical depression and for social dysfunction in excess of that caused by a current major depression.