A new study provides the first direct evidence that experiencing acute trauma can cause the onset of obsessive-compulsive disorder or make existing symptoms worse. Following the October 7th attacks in Israel, researchers found that survivors directly exposed to the violence were nearly six times more likely to develop symptoms consistent with obsessive-compulsive disorder compared to a group that was not directly exposed. The research was published in the journal Psychotherapy and Psychosomatics.
For many years, scientists have observed a connection between trauma and obsessive-compulsive disorder. Studies have shown high rates of post-traumatic stress disorder in people who also have obsessive-compulsive disorder, and vice versa. People with obsessive-compulsive disorder often report a history of traumatic events.
However, this connection has been a bit of a “chicken or egg” puzzle. It was unclear if trauma could directly cause obsessive-compulsive disorder, or if people with obsessive-compulsive disorder were simply more vulnerable to the effects of trauma. No previous study had been able to show a direct causal link where a specific traumatic event led to the emergence of the disorder.
The tragic events of October 7th in Israel presented a unique and unfortunate natural experiment. The attacks created two distinct groups of people within the same country. One group consisted of residents of the ‘Gaza envelope’ communities who experienced intense, direct trauma for hours, including witnessing violence and death and facing immediate threats to their own lives.
A second group consisted of people living elsewhere in Israel who were not directly attacked but experienced the events through news reports, rocket alerts, or having friends and family in the affected areas. This situation allowed researchers to compare the psychological outcomes of a group with extreme, direct trauma to a matched group with more indirect exposure.
The research team, led by Professor Eyal Kalanthroff of the Hebrew University of Jerusalem and Professor Helen Blair Simpson of Columbia University, sought to understand if this severe, acute trauma could lead to new or worsened obsessive-compulsive symptoms. They hypothesized that the directly affected group would show higher rates of these symptoms and that this increase would be linked to the severity of their post-traumatic stress disorder symptoms.
To investigate this, the researchers recruited 132 Israeli adults between four and six months after the attacks. The study included two groups of 66 people each. The first group was composed of survivors who were residents of towns in the Gaza envelope. All individuals in this group were present in their homes during the attacks, had a family member or friend who was killed, injured, or kidnapped, and had been evacuated from their homes for months.
The second group served as a control. It consisted of 66 people who lived in other parts of Israel, more than 12 miles from the Gaza border, where no ground battles occurred. The researchers made sure the two groups were comparable in terms of age, gender, ethnicity, and socioeconomic status, ensuring that the primary difference between them was their level of direct exposure to the traumatic events.
All participants completed a series of questionnaires. One questionnaire confirmed their location and experiences on October 7th to ensure they were in the correct group. Another detailed survey, the Post-Traumatic Stress Disorder Checklist for DSM-5, measured the severity of their post-traumatic stress symptoms related to the attacks.
To measure obsessive-compulsive symptoms, participants filled out the Obsessive-Compulsive Inventory-Revised twice. The first time, they were asked to rate their symptoms over the past month. The second time, they were asked to rate their symptoms as they remembered them in the month before October 7th. This retrospective approach allowed the researchers to establish a baseline and measure any changes. A final questionnaire explored the specific types of symptoms people experienced and asked them to pinpoint when those symptoms first appeared.
The findings were striking. Before October 7th, the self-reported obsessive-compulsive symptom scores were nearly identical and very low for both groups. However, when measured four to six months later, the scores for the directly affected survivor group had increased dramatically. The scores for the control group also rose slightly, but not nearly to the same extent.
Using a strict set of criteria based on the questionnaires, the researchers determined the rate of “probable obsessive-compulsive disorder” in each group. In the group of survivors directly affected by the attacks, nearly 40 percent of individuals met the criteria. This stood in stark contrast to the control group, where only 7 percent met the same criteria.
The study then examined where these symptoms came from. Among the survivors, 24 percent of the entire group were classified as having “new onset” symptoms, meaning their significant obsessive-compulsive symptoms appeared for the first time only after the attacks. In the control group, only one person, representing less than 2 percent, fell into this category. Additionally, for participants who had some pre-existing symptoms, the trauma had a clear impact. Of the survivors with prior symptoms, nearly all reported that their symptoms had become worse since the attacks.
The researchers also explored the role of post-traumatic stress disorder. They found that being in the directly affected group was strongly associated with higher scores on the post-traumatic stress disorder checklist. A statistical analysis revealed that the severity of post-traumatic stress disorder symptoms helped explain the connection between being directly exposed to trauma and the likelihood of developing probable obsessive-compulsive disorder. This suggests that trauma severe enough to cause symptoms of post-traumatic stress may also be a powerful trigger for obsessive-compulsive symptoms. The authors noted that the most common new symptom to emerge was compulsive checking, which may be linked to the specific trauma of violent home invasions.
The study has some limitations, which the authors acknowledge. The research relied on self-report questionnaires rather than clinical interviews conducted by a psychiatrist or psychologist. Additionally, the assessment of symptoms before the trauma was retrospective, meaning participants had to rely on their memory, which can sometimes be imperfect. The researchers attempted to strengthen their conclusions by using multiple questionnaires and setting a high threshold for what they considered clinically meaningful symptoms.
Future research will be needed to follow trauma survivors over a longer period to see if these new symptoms persist, resolve, or change over time. It will also be important to understand which individuals are most at risk of developing obsessive-compulsive disorder after a traumatic experience. Despite the limitations, the study’s findings have significant implications. They suggest that healthcare professionals working with trauma-exposed populations should screen not only for post-traumatic stress disorder but also for obsessive-compulsive disorder. Recognizing that severe stress can trigger these symptoms is the first step toward providing proper support and treatment for all of trauma’s hidden psychological wounds.
The study, “Acute Trauma and OCD: Evidence from October 7th, 2023,” was authored by Eyal Kalanthroff, Shir Berebbi, Mor David, and Helen Blair Simpson.