The duration of untreated illness (DUI), defined as the interval between the onset of a disorder and the first adequate treatment, has been increasingly investigated as a predictor of outcome in psychotic disorders. However, few data are available on the impact of DUI on the outcome of the obsessive-compulsive disorder.

This study aimed at investigating: 1) patients'socio-demographic and clinical characteristics which influence duration of untreated illness in OCD; 2) the effect of duration of untreated illness on outcome.

Eighty-three outpatients fulfilling DSM-IV criteria for OCD were recruited and prospectively followed up for 3 years. Baseline information, demographic and clinical characteristics, were collected by standardized instruments. Obsessive-compulsive symptoms were assessed using Yale-Brown Obsessive Compulsive Scale (Y-BOCS). Fifty-nine patients completed the follow-up.

Recruited patients were predominantly male (52%), with a mean age of 31.5 (SD = 10.2) years, 11.2 (SD = 3.9) years spent in general education. Fifty-two per cent of them were married and 50.6% were employed. The mean DUI was 7.3 (SD = 5.8) years. Patients with a DUI > 2 years had a later onset of OCD, a familiarity for affective disorders, and showed an higher frequency of aggressive obsessions. At completion of the follow-up, these patients showed a worse clinical outcome and more frequently did not achieve remission.

DUI has a considerable impact on outcome of obsessive-compulsive disorder. Being DUI a modifiable prognostic factor, programs aimed to early detection and treatment of OCD could substantially reduce personal, social and economical burden related to this disorder.