The dreary debate about genes versus environment tends to be especially obfuscated around the nurturance issue, for reasons I’ve outlined earlier in this blog.
Here is a wonderful meta-analytic study by Bentall (and colleagues) himself, a psychiatrist I respect greatly. Check out the stuff below. I’ve cut and pasted it directly from the site.
http://schizophreniabulletin.oxfordjournals.org/content/early/2012/03/28/schbul.sbs050.full Schizophr Bull (2012) doi: 10.1093/schbul/sbs050 First published online: March 29, 2012
Childhood Adversities Increase the Risk of Psychosis: A Meta-analysis of Patient-Control, Prospective- and Cross-sectional Cohort Studies
Filippo Varese†,1,2, Feikje Smeets†,3, Marjan Drukker3, Ritsaert Lieverse3, Tineke Lataster3, Wolfgang Viechtbauer3, John Read5, Jim van Os*,3,4 and Richard P. Bentall1
Evidence suggests that adverse experiences in childhood are associated with psychosis. To examine the association between childhood adversity and trauma (sexual abuse, physical abuse, emotional/psychological abuse, neglect, parental death, and bullying) and psychosis outcome, MEDLINE, EMBASE, PsychINFO, and Web of Science were searched from January 1980 through November 2011. We included prospective cohort studies, large-scale cross-sectional studies investigating the association between childhood adversity and psychotic symptoms or illness, case-control studies comparing the prevalence of adverse events between psychotic patients and controls using dichotomous or continuous measures, and case-control studies comparing the prevalence of psychotic symptoms between exposed and nonexposed subjects using dichotomous or continuous measures of adversity and psychosis. The analysis included 18 case-control studies (n = 2048 psychotic patients and 1856 nonpsychiatric controls), 10 prospective and quasi-prospective studies (n = 41 803) and 8 population-based cross-sectional studies (n = 35 546). There were significant associations between adversity and psychosis across all research designs, with an overall effect of OR = 2.78 (95% CI = 2.34–3.31). The integration of the case-control studies indicated that patients with psychosis were 2.72 times more likely to have been exposed to childhood adversity than controls (95% CI = 1.90–3.88). The association between childhood adversity and psychosis was also significant in population-based cross-sectional studies (OR = 2.99 [95% CI = 2.12–4.20]) as well as in prospective and quasi-prospective studies (OR = 2.75 [95% CI = 2.17–3.47]). The estimated population attributable risk was 33% (16%–47%). These findings indicate that childhood adversity is strongly associated with increased risk for psychosis.
Adverse childhood events including trauma is a common experience worldwide, with some estimates suggesting that about a third of the general population may be affected.1 Evidence suggests that its effects in adulthood may include a range of negative social outcomes, including higher criminality,2 a lower educational level3 and lower general health and well-being. Adverse childhood events have also been related to a greater risk of psychiatric disorder1,4,5 and, especially given its high prevalence, it is likely that it is an important determinant of mental ill-health.6
A growing number of methodologically sound studies have examined child maltreatment (eg, sexual abuse, physical abuse, emotional/psychological abuse and neglect), peer victimization (eg, bullying), and experiences of parental loss and separation as risk factors for psychosis and schizophrenia. Nevertheless, the association between adverse childhood events and psychosis has been a topic of enduring controversy. Only narrative reviews have so far attempted to synthesize these findings, with inconsistent conclusions.7–9 Therefore, a systematic quantitative synthesis of the existing data is required.
The present study presents a quantitative review and meta-analysis of the available empirical literature, examining the magnitude and consistency of the effects of different, widely-examined types of adversity and trauma observed in: (i) prospective cohort studies, (ii) large population-based cross-sectional studies, and (iii) case-control studies.