Reporting their work in the American Journal of Medical Genetics, the researchers revealed that they combined data from the latest large-scale international gene hunting studies for bipolar disorder with information from their own studies, which helped them identify the best candidate genes for the illness.
Dr. Alexander B. Niculescu III, an assistant professor of psychiatry and director of the laboratory of neurophenomics at the IU School of Medicine, said that his team mined the data from the genome-wide association studies and other study results on the levels of gene activity in human blood samples and in animal models.
He said that genes with the highest levels of prominence were determined to be the most active in contributing to the disorder.
He added that analysing the working of those genes, the team were able to create a comprehensive biological model of bipolar disorder.
"Based on our work, we now project that there will be hundreds of genes - possibly as much as 10 percent of the human genome - involved in this illness," said Dr. Niculescu.
"Not all genetic mutations will occur in every individual with bipolar disorder. Different individuals will have different combinations of genetic mutations. This genetic complexity is most likely what made past attempts to identify genes for the disorder through genetic-only studies so difficult and inconsistent."
Comparing the process adopted by his team with a Web search, Dr. Niculescu said: "The process was similar to a Google approach, the more links there are to a page on the Internet, the more likely it is to come up at the top of your search list. The more experimental lines of evidence for a gene, the higher it comes up on your priority list of genes involved in the disorder."
The researcher highlighted the fact that there have been few statistically significant findings in searches of the human genome, as it applies to bipolar disorder, to date.
"By integrating the findings of multiple studies, we were able to sort through, identify genes that were most likely to be involved in bipolar disorder, and achieve this major breakthrough in our understanding of the illness," he added.
Bipolar disorder, sometimes called manic depression, is a serious illness that causes patients to experience mild or dramatic mood swings, shifts in energy, and a diminished capacity to function.
Dr. Niculescu said that his team's work could open exciting avenues for psychiatric researchers and clinicians, as well as for patients and their families.
"First and foremost, these studies will lead to a better understanding of bipolar and related disorders. Second, the researchers now plan to study individuals to see which combination of genes is present in individuals to come up with a genetic risk score," he said.
He revealed that the purpose behind the study was to be able to apply the risk score to test individuals even before the illness manifests itself for preventive measures - such as lifestyle changes, counselling, low-dose medications - or to delay or stop the illness from developing.
"Third, in individuals who already have the illness, genetic testing in combination with blood biomarkers for the disease, could help determine which treatments works best so personalized treatments could be developed," Dr. Niculescu said.