Supplementary Material for: Acute Trauma and OCD: Evidence from October 7th, 2023

Exposure to trauma has been theorized to contribute to the onset and exacerbation of obsessive-compulsive disorder (OCD), yet direct empirical evidence remains limited. This study examined whether individuals directly affected by the trauma of October 7th, 2023, in Israel exhibited higher rates of new-onset or worsening OCD symptoms compared to controls who were not directly affected. A total of 132 adults participated, including 66 survivors from the Gaza envelope who experienced direct exposure to the attacks and 66 matched controls from other areas of Israel who were not directly affected. Data on OCD and PTSD symptoms were collected approximately 4–6 months after the events. Results revealed significantly higher OCD symptoms in the directly affected group and PTSD symptom severity partially mediated the relationship between trauma exposure and increased OCD symptoms. Notably, 39% of individuals in the directly affected group met a priori criteria for probable OCD, 24% reported new-onset symptoms after October 7th, and most others reported worsening of existing symptoms. These findings provide the first direct evidence that acute trauma can trigger new-onset and worsening OCD symptoms. Consistent with the diathesis-stress model, the results underscore the role of environmental stressors in OCD etiology and highlight the need for screening for OCD in trauma-exposed populations.