Familial transmission of psychosis shows subtype specificity
MedWire News: Study findings suggest specificity for the familial transmission of schizophrenia-psychosis spectrum (SPS) disorders and affective psychoses (APs).
The results show that individuals born to parents with SPS disorders are approximately six times more likely to develop SPS disorders than individuals born to mentally healthy parents, while the risk for AP among individuals born to parents with AP is increased 14 fold.
Jill Goldstein, from Brigham and Women’s Hospital in Boston, Massachusetts, USA, and colleagues note that there was some cross-disorder risk, but it was not as high as that within each psychosis type.
The researchers used data from the High-Risk Study of the New England Family Study for 203 high-risk individuals born to 159 parents with diagnoses of psychoses, of whom 59 had SPS disorders and 100 had APs, along with 147 individuals born to 114 parents without psychoses.
The study prospectively observed offspring from their mothers’ pregnancy through to adulthood (age ≥40 years), and provides DSM-IV diagnoses for both parents and adult offspring.
In all, 28 of the second-generation individuals developed psychosis in adulthood; 12 developed SPS disorders and 16 APs.
Overall, the prevalence of any psychoses was 9.9% among individuals born to parents with SPS disorders and 13.6% for those born to parents with APs, compared with 2.0% among individuals born to mentally healthy parents.
Among individuals who developed SPS disorders, 8.5% were born to parents with SPS disorders, 3.0% to parents with APs, and 1.4% to mentally healthy controls. For the individuals who developed APs, 10.6% were born to parents with APs, and 1.4% and 0.7% to parents with SPS disorders and mentally healthy controls, respectively.
Multivariate analysis showed that parental SPS disorders significantly increased the offspring’s risk for the condition, at a relative risk of 5.5, whereas the relative risk for APs in offspring of 2.2 was not significant. The same pattern was seen for parental APs, which significantly increased the offspring’s risk for APs but not SPS disorders, at relative risks of 14.0 and 2.1, respectively.
“The magnitude of the risks within each diagnostic grouping are much higher than the cross-disorder risk estimates for both groups,” say Goldstein et al in the Archives of General Psychiatry.
“This suggests, at least, that there is some cross-disorder risk but not as high as within psychosis type.”
The researchers therefore propose that clinical phenotypes are relatively specifically linked within families to type of psychosis.
They add, however, that “this does not rule out the possibility that there will be overlapping neural phenotypes… a question that is under active investigation by our group.”
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By Lucy Piper