Psychology: New Gene for Bipolar Disorder Discovered

Photo: In the lab

Prof. Nöthen in his laboratory; © Volker Lannert/Uni Bonn

Under the direction of scientists from the University of Bonn Hospital, the Central Institute of Mental Health of Mannheim and the University of Basel Hospital, an international collaboration of researchers discovered two new gene regions which are connected with the prevalent disease.

In this unparalleled worldwide study, the scientists are utilizing unprecedented numbers of patients. Throughout the course of their lives, about one percent of the population suffers from bipolar disorder, also known as manic-depressive disorder. The patients undergo a veritable rollercoaster of emotions:

During extreme shifts, they experience manic phases with delusions of grandeur, increased drive and a decreased need for sleep as well as depressive episodes with a severely depressed mood to the point of suicidal thoughts. The causes of the disease are not yet fully understood, however in addition to psychosocial triggers, genetic factors play a large role.

"There is no one gene that has a significant effect on the development of bipolar disorder," says Prof. Markus M. Nöthen. "Many different genes are evidently involved and these genes work together with environmental factors in a complex way."

In recent years, scientists at the Institute of Human Genetics were already involved in decoding several genes associated with bipolar disorder. The researchers are now using unprecedented numbers of patients in an international research collaboration:

New genetic data from 2266 patients with manic-depressive disorder and 5028 control persons were obtained, merged with existing data sets and analyzed together. In total, data on the genetic material of 9747 patients were compared with data from 14,278 healthy persons. "The investigation of the genetic foundations of bipolar disorder on this scale is unique worldwide to date," says Prof. Marcella Rietschel from the Central Institute of Mental Health of Mannheim.

The search for genes involved in manic-depressive disorder is like looking for a needle in a haystack. "The contributions of individual genes are so minor that they normally cannot be identified in the 'background noise' of genetic differences," explains Prof. Sven Cichon from the University of Basel Hospital.

Only when the DNA from very large numbers of patients with bipolar disorder are compared to the genetic material from an equally large number of healthy persons can differences be confirmed statistically. Such suspect regions which indicate a disease are known by scientists as candidate genes.

Using automated analysis methods, the researchers recorded about 2.3 million different regions in the genetic material of patients and comparators, respectively. The subsequent evaluation using biostatistical methods revealed a total of five risk regions on the DNA associated with bipolar disorder.; Source: University of Bonn Hospital