The longitudinal association between psychotic experiences, depression and suicidal behaviour in a population sample of adolescents

Whilst psychotic experiences are associated with suicidal behaviour in a number of studies the value of psychotic experiences for the prediction of suicidal behaviour and the role of depressive symptoms in this relationship is not clear. We examined the association between psychotic experiences and subsequent suicidal behaviour and examine the role of depressive symptoms in this relationship. Psychotic experiences and depressive symptoms at age 12 and 16 years, and suicidal behaviour at age 16 years were assessed in participants (prospective analysis n = 3171; cross-sectional analysis n = 3952) from a population-based cohort. Psychotic experiences (OR 1.75 95 % CI 1.20, 2.54) and depression (OR 3.97 95 % CI 2.56, 6.15) at 12 years were independently associated with suicidal behaviour at 16 years after adjustment for confounding. There was no evidence that the relationship between psychotic experiences and suicidal behaviour was stronger in participants who were also depressive. A ROC analysis showed that adding information on psychotic experiences to measures of depressive symptoms had hardly any effect on improving prediction of suicidal behaviour (AUC increased from 0.64 to 0.65). Whereas adding a measure of depressive symptoms to the measure of psychotic experiences improved prediction substantially (AUC 0.56-0.65). Psychotic experiences and depression are independently associated with suicidal behaviour although the association with depression is substantially stronger. Psychotic experiences alone are not a strong predictor of later suicidal behaviour and add little to predicting the risk of suicidal behaviour over and above the information provided by depressive symptoms.