Genetics, trauma independently influence subthreshold psychosis

By Ingrid Grasmo, medwireNews Reporter

Study findings published in Acta Psychiatrica Scandinavica confirm that both genetics and environmental factors such as trauma independently influence the development and persistence of subthreshold psychotic symptoms.

"These results are in line with recent findings that a substantial proportion of schizophrenia incidence, at the population level, is attributable to non-psychotic disorders in first-degree relatives," say Johanna Wigman (University of Utrecht, the Netherlands) and colleagues.

Given that not all individuals who experience trauma develop psychosis, genetic liability may play a moderating role, say the researchers. Their study suggests that there is no interaction between these two factors, although they caution that some subgroups of psychotic symptoms contained only a few people, reducing the statistical power of the analysis.

Six-year follow up of 2230 adolescents aged 11 years at study initiation in 2001‑2002 revealed that general parental psychopathology was significantly associated with an 8% increase in the likelihood for being in the highest quintile of Community Assessment of Psychic Experiences (CAPE) scores at follow up in 2005‑2007.

In addition, psychotic parental psychopathology significantly predicted persistent psychotic symptoms in children at follow up, increasing this risk 3.72-fold.

Traumatic events before the age of 11 years also played a part, being associated with an increased risk for being in the second to fifth quintiles of CAPE score at follow up, with the increases ranging from 8% to 39%. This association held regardless of whether participants had decreasing, increasing, or persistent symptoms, and was independent of general parental psychopathology.

There was no evidence of interactions between parental psychopathology and trauma. In other words, parental psychopathology did not alter the relationship between childhood trauma and later psychosis, and vice versa.

"Potentially causal effects of childhood trauma act independently of pre-existing genetic liability to increase risk of psychosis and that type, frequency and severity of the trauma are the crucial factors determining risk," conclude the authors.

Future research should aim to replicate the findings in larger samples with more statistical power, focusing on the possible interaction between trauma and liability to psychosis, they add.

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