A comprehensive study of Swedish twins has raised questions about the commonly assumed causal link between adolescent bullying and later development of obsessive-compulsive disorder (OCD).
Published in Molecular Psychiatry, the research indicates that shared genetic factors, rather than bullying alone, may underlie this association.
Researchers analyzed data from over 16,000 twins born in Sweden between 1993 and 2006, combining diagnostic records from the Swedish National Patient Register with responses from the Child and Adolescent Twin Study in Sweden.
At age 15, participants completed a widely used bullying assessment, while OCD symptoms were tracked at ages 18 and 24 using validated clinical scales.
The findings revealed that adolescents who reported being bullied were more likely to later show symptoms of OCD. Among those diagnosed with OCD, 11% had experienced bullying compared to just 4% among peers without the diagnosis. Additionally, those with OCD had higher rates of comorbid anxiety and depressive disorders.
However, when the analysis was broken down by zygosity, a critical pattern emerged. The link between bullying and OCD was observed only in dizygotic (fraternal) twins, who share about 50% of their genetic material, and not in monozygotic (identical) twins, who share 100% of their genes. This divergence suggests that the correlation may be driven by inherited traits rather than environmental experiences alone.
“These results suggest that the association between bullying victimization and OCD/OCS is likely due to genetic confounding and therefore incompatible with a strong causal effect,” the authors wrote. They also point to evocative gene-environment correlations—where genetic predispositions might increase the likelihood of experiencing certain environments, such as being bullied—as a more plausible explanation.
Obsessive-compulsive disorder affects roughly 1–2% of the population and typically begins in adolescence or early adulthood. It is marked by intrusive thoughts (obsessions) and repetitive behaviors (compulsions) that individuals feel driven to perform to alleviate distress. Treatment often involves a combination of cognitive-behavioral therapy and medication, particularly selective serotonin reuptake inhibitors (SSRIs).
While the study offers important insights into the genetic underpinnings of OCD, the researchers caution that the bullying data were self-reported and therefore susceptible to recall bias.
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