Background. The aims of this research were to examine the associations between the personality trait of neuroticism in adolescence and later psychotic symptoms, taking into account potential confounding factors.

Method. Data were gathered over the course of a longitudinal study of a birth cohort of New Zealand born young people (N=1265). Over the course of the study, data were gathered on: (a) neuroticism at age 14; (b) psychotic symptoms predominantly subclinical, assessed on the Symptom Checklist (SCL-90), at ages 18 and 21; (c) a range of potential confounding factors including measures of childhood adversity and co-morbid mental disorders.

Results. Young people in the highest quartile of neuroticism at age 14 had rates of psychotic symptoms that were two to three times higher than those in the lowest quartile. After statistical adjustment for confounding factors, including childhood adversity and co-morbid mental disorders, the association between neuroticism and later psychotic symptoms reduced but remained statistically significant (P<0·05). After adjustment for confounding, young people with high levels of neuroticism had rates of psychotic symptoms that were between 1·5 to 1·8 times higher than those with low levels of neuroticism.

Conclusions. Early neuroticism may be a precursor to the onset of psychotic symptoms. The mechanisms underlying this association are unclear, but may relate to overlapping features between prodromal phases of psychosis and items that measure neuroticism.