Stockholm, Sweden, January 16: Evidence suggests that the world's two major psychotic disorders, schizophrenia and bipolar disorder, are highly heritable and may share a common genetic nature.
The study was the work of Paul Lichtenstien and colleagues from the Karolinska Institute in Stockholm, Sweden.
For the study, the scientists examined the records of 9 million Swedes in around 2 million nuclear families over a period of 30 years. They discovered 35,985 cases of schizophrenia and 40,487 cases of bipolar disorder.
Analyzing the population database, the researchers assessed the risks of the two disorders separately and together for biological, adoptive parents, children, full and half siblings.
The results revealed that first degree relatives of patients with either schizophrenia or bipolar disorder were at higher risk of having these disorders.
A child had 9.9 times more chance of developing schizophrenia if either of its parents were suffering from the ailment. Also, it raised the risk of having bipolar disorder by 5.2 times than someone without a schizophrenic parent.
Having a parent afflicted with bipolar disorder raised the risk of a person by 6.4 times and the risk of developing schizophrenia by 2.4 times, compared to those whose parents did not have this problem.
If brothers or sisters suffered from a psychiatric condition, the odds of the person having mental disorders accelerated. However, with half siblings, the risk was a little lower than with whole blooded siblings.
Heritability for schizophrenia and bipolar disorder was 64 and 59 per cent respectively, and for both together the figure was 63 percent.
Lichtenstien and his team commented that “these results challenge the current nosological dichotomy between schizophrenia and bipolar disorder, and are consistent with a reappraisal of these disorders as distinct diagnostic entities.”
Both schizophrenia and bipolar are mental disorders, the former characterized by abnormalities in perception of reality. It manifests as hallucinations, delusions and paranoia. Bipolar disorder is also called maniac depressive illness. Its symptoms include extreme mood swings, over excitement, elation coupled with severe irritability and depression.
The findings were published in the medical journal The Lancet.
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