Existing data suggest that the duration of untreated illness (DUI) for OCD patients is notably prolonged. Only few studies have investigated whether clinical phenotypes differ in terms of latency to treatment. This study aims to investigate clinical characteristics associated with shorter or longer DUI in OCD patients.

A sample of 316 patients with OCD were consecutively recruited from two OCD Tertiary Clinics in Italy. ​​Sociodemographic and clinical variables were compared between two subgroups based on DUI: Short DUI (sDUI: <4 years) and Long DUI (lDUI: ≥4 years). In addition, multivariable models were performed to examine the independent association of stressful events at onset and sociodemographic factors with DUI.

The sDUI subgroup showed significantly higher rates of stress events at onset (40.8 % vs. 20.8 %, p<.05). Logistic regression confirmed that stressful events were independently associated with a lower likelihood of long DUI (OR = 0.41, 95 % CI 0.20–0.84, p = .016). Higher rates were observed in association with lDUI for obsessions of contamination (47.3 % vs. 29.8 %, p<.005), symmetry (27.4 % vs. 11.9 %, p<.001), somatic (20.5 % vs. 11.9 %, p<.05), and multiple obsessions (42.5 % vs 20.2 %, p<.005). Among the compulsion phenotypes, lDUI patients showed higher rates of compulsive cleaning (52.1 % vs. 35.7 %; p<.005), counting (13.7 % vs. 4.2 %, p<.005), hoarding (11.6 % vs. 5.3 %, p<.05), ordering (28.8 % vs. 15.5 %, p<.005), and repeating rituals (28.1 % vs. 15.5 %, p<.005).

Present findings highlight a significant association between DUI and specific clinical phenotypes in OCD patients. Higher rates of stress events at onset in patients with sDUI suggest that stress events may trigger earlier treatment seeking. These insights underscore the importance of early identification to reduce DUI, potentially improving long-term outcomes.