People with schizophrenia are more likely to report having had a wide range of unhappy childhood experiences than are healthy, age-matched controls, a group of Australian researchers has found.

Childhood adversity has been associated with higher risk for numerous adult psychiatric disorders. Childhood physical abuse, sexual abuse, neglect, and other types of abuse have been shown in a recent meta-analysis to be associated with an increase in the risk of psychosis (Schizophr. Bull. 2012 March 29 [doi:10.1093/schbul/sbs050]). This new study adds to the catalog of childhood hardships seen as bearing on risk for schizophrenia (J. Psychiatr. Res 2012;46:600-7).

Ph.D. candidate Kathryn L. McCabe and her colleagues used data from 675 adults (aged 18-65 years), all of whom previously had been recruited as part of a national schizophrenia study cohort, the Australian Schizophrenia Research Bank.

Of the subjects, 408 were diagnosed with schizophrenia (268 men, 140 women). The remaining 267 (116 men, 151 women) were healthy, age-matched controls. Subjects and controls completed extensive clinical interviews that included the use of a standardized childhood adversity questionnaire measuring 19 types of adversity, from sibling loss to the feeling that parents “did not do their best for me,” reported Ms. McCabe of the Schizophrenia Research Institute in Darlinghurst, New South Wales, and her colleagues. Schizophrenia subjects reported higher rates of abusive, neglectful, and dysfunctional parenting than did controls. After controlling for age, sex, and education, the researchers found that subjects with schizophrenia were significantly more likely to report experiencing childhood trauma than were controls (86.8% vs. 69.5%; odds ratio, 2.87; 95% confidence interval, 1.95-4.23; P less than .001), and to report suffering more of the types of 19 adversities listed in the questionnaire (mean, 5.4 vs. 2.3), wrote Ms. McCabe, who also is affiliated with the University of Newcastle (New South Wales).

Humiliation by a parent, growing up in a household characterized by conflict, and witnessing the physical or sexual abuse of others all were associated with statistically significant increases in risk. Having had a parent who was “not affectionate at all” was associated with an OR of 2.89 (95% CI, 1.84-4.52; P less than .001), the researchers found, whereas verbal abuse by a parent was associated with an OR of 2.32 (95% CI, 1.53-3.51; P less than .001).

Severity of positive symptoms – including auditory hallucinations, delusions, and disordered thoughts – was also seen as correlating with numbers of adversities reported. No relationship was seen between reported childhood adversities and negative symptoms of schizophrenia, which have been shown in studies to antedate the onset of psychosis, the researchers wrote, “and may therefore be likely to reflect neurodevelopmental dysfunction that is a core component of the schizophrenia syndrome and less subject to environmental influences.”

The researchers noted that despite their study’s limitations – which included the fact that experiences of adversity were self-reported and subject to recall bias, and also that the cohort of schizophrenia patients was relatively high functioning – “the rate of childhood adversity reported in this sample was high, suggesting greater exposure to adverse childhood events among participants with schizophrenia in comparison with healthy controls. These findings are consistent with previous research indicating that childhood adversity is related to subsequent development of a range of mental illnesses, including schizophrenia.”

The research was funded by the National Health and Medical Research Council of Australia, the Pratt Foundation, Ramsay Health Care, the Viertel Charitable Foundation, and the Schizophrenia Research Institute. None of the researchers declared conflicts of interest.