Evidence of the direct contribution of exposure to bullying in childhood to symptoms of depression and anxiety, as well as indications of a contribution to paranoid thoughts and cognitive disorganization were reported in a study published in JAMA Psychiatry.

The study by Jean-Baptiste Pingault, Ph.D., of University College London, England, and coauthors included 11,108 twins who were an average age of 11 when they were first assessed and about 16 at the last assessment. Mental health assessments at those ages included anxiety, depression, hyperactivity and impulsivity, inattention, conduct problems and psychotic-like experiences, such as paranoid thoughts or cognitive disorganization. Exposure to bullying was measured using a self-reported peer-victimization scale.

The "twin differences" design of the study used one twin as a control for the other, thereby accounting for shared environmental and genetic sources of other potential mitigating factors.

The study suggests childhood exposure to bullying contributes to multiple mental health issues, particularly anxiety, depression, paranoid thoughts and cognitive disorganization. This dissipated or was reduced after five years.

Limitations of the study include that a twin differences study design does not account for non-shared environmental mitigating factors, which might exaggerate the contribution of childhood exposure to bullying.

"Stringent evidence of the direct detrimental contribution of exposure to bullying in childhood to mental health is provided. Findings also suggest that childhood exposure to bullying may partly be viewed as a symptom of preexisting vulnerabilities. Finally, the dissipation of effects over time for many outcomes highlights the potential for resilience in children who were bullied," the article concludes.

The Twins Early Development Study is supported by program grants from the UK Medical Research Council. This research is funded by grants from the Economic and Social Research Council and MQ: Transforming Mental Health.