Scientists have discovered two new gene regions connected to bipolar disorder that causes extreme mood swings in people.
Researchers were also able to confirm three additional suspect genes for the disorder.
In this "unparallelled worldwide study," the scientists are utilising unprecedented numbers of patients.
Throughout the course of their lives, about one per cent of the population suffers from bipolar disorder, also known as manic-depressive disorder.
The patients undergo a veritable roller-coaster 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.
"Many different genes are evidently involved and these genes work together with environmental factors in a complex way," Professor Markus M Nothen, Director of the Institute of Human Genetics of the University of Bonn Hospital, said.
In total, data on the genetic material of 9747 patients were compared with data from 14,278 healthy persons.
Using automated analysis methods, researchers recorded about 2.3 million different regions in the genetic material of patients and comparators, respectively.
The subsequent evaluation using bio-statistical methods revealed a total of five risk regions on the DNA associated with bipolar disorder.
Two of these regions were newly discovered: The gene "ADCY2" on chromosome five and the so-called "MIR2113-POU3F2" region on chromosome six.
The risk regions "ANK3", "ODZ4" and "TRANK1" have already been described in prior studies.
"These gene regions were, however, statistically better confirmed in our current investigation - the connection with bipolar disorder has now become even clearer," said Nothen.
The researchers are particularly interested in the newly discovered gene region "ADCY2".
It codes an enzyme which is involved in the conduction of signals into nerve cells, researchers said.
The findings appear in the journal Nature Communications.
