Is the familial risk of severe mental disorder broader than we thought? Schiz Bull Jan .2014.

17.01.2014

Offsprings of parents with severe mental disorders have an increased chance of developing the disorder.  Patients and their families would benefit from knowing the exact risk that possibility. It was generally thought that familial risk is diagnosis specific. i.e. children are at risk of the same disorder as their parents. But newer evidence suggest that risk is much broader.

Daniel Rasic, Tomas Hajek, Martin Alda, and Rudolf Uher provide the most up-to-date quantification of  familial risk in this meta analysis.They included all cross-sectional and longitudinal studies addressing the risk of SMI ( Severe Mental Illness: psychotic disorders/ mood disorders).They included only studies that systematically assessed offspring with a valid diagnostic interview at mean age of 10 years or higher. Offsprings had to be recruited through parents only.SMI in offspring was defined as schizophrenia or non affective psychosis, bipolar disorder (I or II) or major depressive disorder.

Results

33 studies met criteria, giving information on 3863 offspring of parents with SMI. Mean age  of off spring at last diagnostic assessment was 21.

1.The probability of offspring of parents with SMI developing SMI themselves was 0.32 (95% CI 0.24–0.42) .

2.Offspring of parents  with SMI had a 2.5-fold increased risk of developing SMI compared with matched control offspring (RR = 2.52, 95% CI 2.08–3.06)

3. 55% of high-risk offspring suffered from any diagnosed mental disorder, with little differences by parental diagnoses.

4. There was evidence for partial specificity with largest RR for schizophrenia among offspring of parents with schizophrenia and largest RR for bipolar disorder among offspring of parents with bipolar disorder.

5. The risk of developing a psychotic or major mood disorder other than the disorder present in parent was increased 1.92 times (95% CI 1.48–2.49, P < .001) among offspring of parents with SMI. For comparison, the risk of the same disorder as diagnosed in the parent was increased by 3.59-fold.

Limitations:

There are only a small number of offsprings studies  ( e.g.:  in schizophrenia offsprings).Most studies made their diagnoses based on single cross-sectional assessment and not all disorders were assessed in most studies. Offspring had not been followed up through the age of peak risk of SMI onset in most studies.  Results thus  should  be considered preliminary.

Conclusion: By early adulthood, the offspring of SMI has a 1-in-3 risk of developing a psychotic or major mood disorder and 1-in-2 risk of developing any mental disorder.There is partial specificity  in schizophrenia and bipolar disorder.However , the familial risk extends across diagnostic boundaries.

Summary of the article:

One thought on “Is the familial risk of severe mental disorder broader than we thought? Schiz Bull Jan .2014.

  1. As quantifying risk attributable to an illness, which attracts lots of stigma with resulting discriminatory social consequence, need to be careful, conclusions thereof (rightly forewarned as preliminary and of low scientific weightage in view of small sample sizes) need to be worded clear of statistic jargon.

    1.The blog conclusion reads……..… By early adulthood, the offspring of SMI has a 1-in-3 risk of developing a psychotic or major mood disorder and 1-in-2 risk of developing any mental disorder

    2. The article conclusion reads…….: Offspring of parents with SMI are at increased risk for a range of psychiatric disorders and one third of them may develop a SMI by early adulthood.

    If one were to believe that such “evidence” is useful in psycho educating patients with healthy children about “risk”, it needs to be stated more clearly. The Cochrane reviews have introduced summaries written in simple plain english for layman on reviews they publish. It may be more difficult here as quantifng risk is very nebulous compared to interpreting intervention-studies which Cochrane does.

    Yet, I feel like warning because stating numbers tend to gloss over the faces behind numbers. I am inclined to think that ,however well scientifically we quantify the risk, a large proportion of children are still not affected without doing any intervention. Profiling “at risk” children for a population level intervention (as against doing so for research purpose) is going to have dubious consequences.

    Reactive depression of children in their care taker role of their parents who are chronically Ill is not just limited to psychiatric illness. That surely broadens the risk of illness but without a genetic component. There is some confounding there, I guess.

    Thanks for this thought provoking review.
    Ramkumar.

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