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Saturday 26th May 2018

Bipolar disorder, schizophrenia 'link'

19th January 2009

Researchers have undertaken the largest study yet that tracks bipolar disorder and schizophrenia within families.


The study indicates that the two psychiatric disorders may share a common cause.

The possible connection between schizophrenia and bipolar disorder has been debated for over a century.

The two disorders have symptoms in common. The manic mood swings characteristic of bipolar disorder resemble the psychosis of schizophrenia.

Recent studies have also indicated that the two are somehow connected by means of a common genetic origin.

However, until now, studies in families did not support this conclusion.

Earlier studies found no increase in bipolar disorder in the families of schizophrenics, and no decrease where schizophrenia was absent.

Researchers in Sweden attempted to resolve the enigma by means of data gathered widely from the national health registry and hospital records.

From 1973 to 2004, 9 million people from 2 million families were analysed.

The goal was to determine the risk for schizophrenia and bipolar disorder by studying patients and relatives by either blood or marriage.

The number of people with schizophrenia numbered close to 36,000 and the number of those diagnosed with bipolar disorder 40,500 approximately.

The patients under study had either one or both of the disorders.

There was a significant increase in the probability of having one of the disorders among adopted children with a biological parent affected by the other.

The researchers found increased risk in first-degree relatives: parents, siblings, or offspring.

Affected siblings in particular altered these probabilities.

Having a full sibling with schizophrenia increased the probability that someone would have it by a factor of eight or nine.

Having a half sibling by the same mother increased the probabilities by 3.6, and having a half sibling by the same father by 2.7.

It went up by a factor of four if the person had a full sibling with bipolar disorder, 4.5 if they shared the same mother, and 2.4 if they shared the same father.

By contrast, environmental factors were found to have less of a probabilistic effect.

Christina Hultman, PhD said that it is time that people rethink the way they view these disorders.

She said that it is clear that people need more genetic studies to help better understand shared risks.

Michael Owen of Cardiff University said that previous studies were too limited in scale to understand the genetic commonalities between the two disorders.

Owen said that the finding has major implications for the management of patients.

He said that when someone receives a diagnosis of schizophrenia, clinicians often overlook mood disorder and other symptoms they feel don't fit with that diagnosis.

He said that the same happens with psychotic symptoms reported in people labelled as having bipolar disorder, and that doctors should realise that as time passes, the symptoms often change.

John Krystal of Yale University Medical Center said that upcoming research could profoundly affect how these two disorders are handled by psychiatrists.


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