The role of bullying in psychosis: a novel analysis of national survey data using Directed Acyclic Graphs.

Speaker:  Professor Paul Bebbington, UCL Division of Psychiatry

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Abstract: Complex interactions between multiple variables in large datasets create difficulties for causal inference. Directed Acyclic Graphs (DAGs) represent a considerable advance. They use Bayesian probabilistic models to capture the dependence structure of multiple variables and provide robust conclusions about causal effects. To illustrate this  we investigated putative mediators of the association between bullying victimization and persecutory ideation, using data from the 2007 English National Surveys of Psychiatric Morbidity. Bullying had direct effects on worry, persecutory ideation, mood instability and drug use. Depression, sleep and anxiety lay downstream, and therefore did not mediate the link between bullying and persecutory ideation. Bullying led to hallucinations indirectly, via persecutory ideation and depression. An equivalent DAG analysis of the 2000 dataset suggested the technique generates stable results.