Psychotic experiences show shared genetic liability

Study findings provide support for psychotic experiences being an early marker of increased risk of psychosis transition and an important intermediary phenotype in transdiagnostic research on psychosis.

The findings, from the Copenhagen Child Cohort 2000 (CCC2000) study, showed a significant association between psychotic experiences in preadolescents and a history of psychosis among first-degree relatives.

Among 1632 children, aged 11 to 12 years, from the general population, 21 (1.3%) had a first-degree relative with a psychotic disorder and 172 (10.5%) had a history of psychotic experiences.

Binomial logistic regression analysis showed that the risk of a psychotic experience was increased 3.29-fold if adolescents had a first-degree relative with a psychotic disorder.

By contrast, there was no significantly increased risk of psychotic experiences among the 192 (11.8%) adolescents who had a first-degree relative with a nonpsychotic psychiatric disorder (relative risk=1.20), or for the 118 (7.2%) adolescents with a second-degree relative with a psychotic disorder.

“The discrepancy with regard to the findings of a significant effect of psychotic disorder in first-degree but no effect of any disorders in second-degree relatives may reflect the fact that the psychiatric history is a proxy measure of the familial liability comprising both genetic and environmental factors”, say the researchers.

Led by Pia Jeppesen (Mental Health Services, The Capital Region of Denmark, Glostrup), the team reports that the risk of psychotic experiences associated with high familial loading of psychosis in first-degree relatives was highest for combined hallucinations and delusions, the risk of which was increased 5.90-fold.

But in sensitivity analyses examining psychotic experiences only in the past month, familial load had the greatest effect on isolated hallucinations, which the researchers say “may reflect that the combined type of PE [psychotic experiences] captures the development of secondary delusional ideas, which may need a longer observation time to develop.”

Jeppesen et al say their data “support the hypothesis of a familial load of psychosis being significantly associated with PE in offspring, but only with regard to the load in first-degree relatives.”

And suggest that “early manifestations of PE may share some of the genetic liability underlying the transdiagnostic dimension of psychosis.

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