The findings are being presented today at the European Society for Child & Adolescent Psychiatry Congress taking place in Dublin and appear in this month's edition of the American Journal of Psychiatry.

This was a collaborative project between the National Suicide Research Foundation (Cork) and RCSI with funding from the Health Research Board (HRB) and the European Union Framework 7 Programme. The researchers undertook a nationally representative prospective cohort study of 1,112 school-based adolescents aged 13-16 years, and assessed them at baseline, three-months and 12-months for childhood trauma (defined as physical assault and bullying) and psychotic experiences.

ProfessorMary Cannon, HRB Clinician Scientist and Senior Investigator, Department of Psychiatry, RCSI said "Our findings are the first to show there is direct evidence between exposure to childhood trauma and psychotic experience. Furthermore, it showed that the cessation of traumatic experiences was associated with a significant reduction in the incidence of psychotic experiences. These findings place new weight on calls for more comprehensive preventions and intervention strategies against childhood trauma in the community from abuse at home and bullying in schools.

The study aimed to determine whether childhood trauma could be considered a cause of psychotic experiences. In order for something to be genuinely considered 'a cause', it has to show a number of characteristics such as, a strength of association -- namely the stronger the association the more likely that it is causal; a dose-response relationship -- as the dose increases, so should the odds of the outcome or cessation of exposure -- if exposure ceases or decreases, then the odds of the outcome should also cease or decrease.

Professor Cannon, continued "Our findings showed a clear relationship between exposure to childhood trauma and the onset of psychotic symptoms because the strength of the relationships was large in terms of odds ratios. We also saw a dose-response relationship with the odds of psychotic symptoms increasing in line with increasing levels of bullying."

Dr Ian Kelleher, Lead Investigator, Department of Psychiatry, RCSI said "Our analysis shows, we believe for the first time, that cessation of traumatic experiences predicted a significantly reduced incidence of psychotic experiences compared to individuals for whom the traumatic experiences continued. This is a very encouraging finding and suggests that population based approaches could have a large impact reducing the prevalence of psychotic symptoms."

"The research found that 'classmates' were the largest group inflicting physical harm. Additionally, as most bullying taking place within the school, teacher training could have a very important role to play in reducing this harm," said Dr Kelleher.

Dr Helen Keeley and Dr Paul Corcoran of the National Suicide Research Foundation were co-investigators on this research.