By Joanna Lyford, Senior medwireNews Reporter
Around one in three children of parents with a severe mental illness (SMI) – schizophrenia, bipolar disorder, or major depressive disorder – will develop such a disorder themselves by early adulthood, a meta-analysis has found.
While the children were most likely to develop the same condition suffered by their parent, familial transmission was only partly diagnosis-specific.
“As a result, the total risk of SMI and any mental illness in offspring of parents with psychotic or major mood disorders are higher than previously thought,” write Rudolf Uher (Dalhousie University, Halifax, Nova Scotia, Canada) and co-authors. “This should be reflected in genetic counseling and information provided by clinicians.”
The researchers identified 33 studies involving 3863 children of parents with an SMI (high-risk children) and 3158 children of parents without an SMI (controls).
Overall, 55% of high-risk children suffered from a diagnosed mental health disorder. Meta-analysis found that high-risk children were 2.5 times more likely to develop an SMI in their lifetime compared with control children.
High-risk children had an 18% chance of developing an SMI between the age of 10 and 19 years and a 32% chance once they were aged 20 years and above.
There was evidence of partial specificity of familial transmission, note Uher et al, such that children who developed an SMI were most likely to have the same diagnosis as their parent (risk ratio[RR]=3.59).
However, there was also evidence of general familial risk, meaning that high-risk children were at increased risk for developing any of the disorders studied (RR=1.92).
Uher et al say that their analysis suggests that the widely cited figure of one in 10 for the risk for familial transmission of SMIs is an underestimate, and that the real figure is around one in three.
However, they warn that their findings should be considered preliminary and conclude: “Cross-diagnostic research may be needed to advance the knowledge of etiology and plan effective preventive interventions.”
The study is published in Schizophrenia Bulletin.
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