SYDNEY, May 14 (Xinhua) -- Aussie researchers have identified 70 previously unknown genes linked to the development of serious mental health disorders schizophrenia, bipolar disorder, depression and Attention Deficit Hyperactivity Disorder (ADHD).

Led by the head of QIMR Berghofer's Translational Neurogenomics Group, Professor Eske Derks, the study identified how those 70 new genes, along with 261 others already linked to mental illness, increased the risk of developing a disease.

The research adds to a growing body of evidence which suggests that genetic risk factors, as well as environmental factors such as stress and trauma, can lead to schizophrenia, bipolar disorder, depression and ADHD.

"In this study, we are homing in on the biological causes of these mental illnesses," Derks said.

"Recent studies have found associations between the disorders and large regions of the genome, but they didn't reveal which particular genes were responsible or how the genes' activity affected the risk of developing a mental illness," Derks said.

The team looked at the genetic data from tens of thousands of people, comparing those diagnosed with a mental illness, to data from those without.

"For schizophrenia for example, we looked at the genetic data from about 40,000 patients and compared it to data from about 65,000 control samples from people without the disorder," Derks said.

"Through this process we identified 275 genes whose activity levels contribute to the risk of schizophrenia, 13 genes whose expression is associated with bipolar disorder, 31 genes involved in depression and 12 for ADHD," Derks said.

The study provides more evidence regarding the genetic basis for these diseases, giving scientists a better understanding of which drugs and treatments are best suited to manage them.