Familial risk for psychosis does not account for the association between abuse during childhood and the later development of schizophrenia, a study suggests.
Patients with psychosis were 3.79-fold more likely than controls to report severe maternal physical abuse beginning before the age of 12 years, after adjusting for age, ethnicity, gender, and parental social class, say Helen Fisher (King’s College London, UK) and colleagues. But adjusting for a history of psychosis in a parent only slightly attenuated the association, to give a 3.31-fold increase.
Thus, “the findings of the current study tentatively suggest that preventing exposure to physical abuse from mothers during childhood, stopping its recurrence, or at the very least tackling the consequences of exposure to this form of abuse, may reduce the likelihood of psychotic disorders developing,” says the team.
The researchers had thought that genetic psychosis risk could underlie the association between childhood abuse and schizophrenia, because a “parent with psychosis may provide both a risky childhood environment and the genetic propensity for the disorder to their offspring.”
Alternatively, childhood abuse may be a trigger leading to psychosis in people at genetic risk, which “could explain why not all individuals exposed to maltreatment go on to develop psychotic disorders,” Fisher et al write in Schizophrenia Bulletin.
Indeed, as well as having an increased likelihood for previous severe abuse (assessed with the Childhood Experience of Care Abuse Questionnaire), the 172 patients with psychotic disorders had a sevenfold increased likelihood for having at least one first-degree relative with a psychotic disorder, relative to 246 mentally healthy controls.
This implied a gene–environment interaction, which was supported by a threefold greater likelihood for parental psychosis in psychosis patients with a history of maternal abuse, relative to those without. However, adjusting for parental psychosis had only a small effect on the strength of the association between maternal abuse and psychosis.
And in stratified analyses, maternal abuse was significantly associated with psychotic disorders both in patients with and without a family history of mental illness (psychosis, depression, and mania).
“Therefore, together these findings suggest that preventing or at least stopping continued exposure to physical abuse could prevent the onset or persistence of psychosis,” concludes the team.
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