Researchers from the University of Bonn and the Central Institute of Mental Health in Mannheim have discovered that the NCAN gene can result in the manic symptoms of bipolar disorder.
Individuals with bipolar disorder suffer from depression and suicidal thoughts during depression phases and during manic episodes they face restlessness, euphoria, and delusions of grandeur.
"It has been known that the NCAN gene plays an essential part in bipolar disorder. But until now, the functional connection has not been clear," Professor Markus M Nothen from the University, said.
The researchers evaluated the genetic data and the related descriptions of symptoms from 1,218 patients with differing ratios between the manic and depressive components of bipolar disorder.
Using the patients' detailed clinical data, the researchers tested statistically which of the symptoms were especially closely related to the NCAN gene.
"Here it became obvious that the NCAN gene is very closely and quite specifically correlated with the manic symptoms," Dr Marcella Rietschel from the Central Institute of Mental Health in Mannheim, said in a statement.
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According to the data the gene is, however, not responsible for the depressive episodes in bipolar disorder.
A team working with Dr Andreas Zimmer, Director of the Institute of Molecular Psychiatry at the University of Bonn, examined the molecular causes effected by the NCAN gene.
The researchers studied mice in which the gene had been "knocked out".
"It was shown that these animals had no depressive component in their behaviours, only manic ones," Zimmer said.
These knockout mice were considerably more active than the control group and showed a higher level of risk-taking behaviour.
In addition, they tended to exhibit increased reward-seeking behaviour, which manifested itself by their unrestrained drinking from a sugar solution offered by the researchers.
The study was published in the The American Journal of Psychiatry.