Childhood trauma and psychosis: a case-control and case-sibling comparison across different levels of genetic liability, psychopathology, and type of trauma.

OBJECTIVE: The associations of two types of childhood trauma (abuse and neglect) with psychosis symptom domains were investigated in subjects with psychotic illness, high psychosis vulnerability, and average psychosis vulnerability.
METHOD: Childhood trauma was assessed with the Childhood Trauma Questionnaire. Symptoms were assessed with the Positive and Negative Syndrome Scale in the patients (N=272) and with the Structured Interview for Schizotypy-Revised in the patients' siblings (N=258), and healthy comparison subjects (N=227).
RESULTS: Childhood trauma was associated with psychotic disorder in a dose-response fashion in the comparison of patients and healthy subjects (adjusted odds ratio=4.53, 95% CI=2.79-7.35). The comparison of siblings and healthy subjects suggested that siblings shared a degree of trauma with the patients (adjusted odds ratio=1.61, 95% CI=0.95-2.61), but the patient-sibling comparison indicated much greater exposure in patients than in siblings (adjusted odds ratio=2.60, 95% CI=1.78-3.78). Childhood abuse but not neglect was associated with positive but not negative symptoms in a dose-response fashion in all three groups. There was no evidence for moderation by sex.
CONCLUSIONS: Discordance in psychotic illness across related individuals can be traced to differential exposure to trauma. The association between trauma and psychosis is apparent across different levels of illness and vulnerability to psychotic disorder, suggesting true association rather than reporting bias, reverse causality, or passive gene-environment correlation. Positive psychotic symptoms in vulnerable individuals may arise as a consequence of the level and frequency of exposure to abuse rather than neglect, suggesting symptom-specific and exposure-specific underlying mechanisms.