New depression genes identified by combining large molecular genetic studies

An international study led by the University Medical Center Groningen (UMCG) has identified new genes that are related to depression. This research is part of a recent series of international studies showing, after years of fruitless attempts, that it is possible to determine the genetic background of psychiatric diseases and problems after all. The scientific journal Molecular Psychiatry published the results of this research today.

It wasn’t until very recently that genetic markers for depression were discovered. The increasingly large studies that include both genetic information and information on depression have particularly led to this success. These studies were preceded by a period of more than 10 years during which researchers were able to map the human genome, but could not yet find a link with depression.

Combining studies of depression, schizophrenia and bipolar disorder

While the UMCG researchers also based their research on very large studies, they took a somewhat different approach: they used data already published by other researchers to find genes. Their approach focused on combining studies on depression with those on two other psychiatric conditions, schizophrenia and bipolar disorder, as these disorders all partly share the same genetic background. The UMCG researchers used the genetic overlap with schizophrenia and bipolar disorder to find new genetic markers for depression. In doing so, they took advantage of the fact that very large studies into schizophrenia and bipolar disorder had already been conducted as well. This proved to be a strong approach for identifying new genetic markers for depression.

New genetic markers for depression

In total, this approach yielded 20 new genetic markers. Finally, the researchers studied an independent sample of participants of the UK Biobank, including both people who suffered from depression and those who did not, to check whether the newly found 20 markers were also associated with depression there. This was indeed the case for 13 markers, 5 of which had already been linked to depression in academic literature, but 8 of which were completely new. Catharina Hartman, one of the principal researchers of the UMCG study, says: ‘I actually no longer expected this recent success. For a long time, we found nothing at all, while there were great achievements for other common complex diseases such as type 2 diabetes and high blood pressure. This had led me to assume that depression and psychiatric disorders in general were too ‘complicated’ to identify any underlying genes.’

Significance for research and treatment

Although the number of new markers is modest, they certainly contribute towards completing the picture. It is remarkable that new findings can be made by combining the results of existing research, i.e. without incurring extra costs and without asking people to make an extra effort by donating biological material and providing information on the symptoms of depression. Principal researcher and genetic epidemiologist Harold Snieder: ‘That is what makes this type of research promising, and its application to other complex mental or physical disorders may lead to further discoveries. Slowly, we are learning more about the underlying biological mechanisms, although there is still a long way to go.’ Nevertheless, the research on the genetic background of psychiatric disorders is finally showing great progress, leaving the researchers optimistic: ‘This genetic research may ultimately contribute a lot to early recognition and the treatment of patients.’