Scottish research team discovers over 100 genetic links responsible for depression

Great strides have been made in search for a cure for depression. Depression affects about one sixth of the word-wide population. Symptoms include low mood, lethargy, diminished libido, no appetite and many more. It is a debilitating psychiatric illness that has long been thought to have genetic as well as external factors such as trauma, bereavement or stress. In some people it only occurs once in their lifetime for a short period of time, for others it remains a chronic condition that can lead to suicide in the worst cases.

The genetic component has been the topic of research for many years. It has been known for a while that a large number of genes are involved in depression, with each only having a very small effect, rather than a single ‘depression gene’. But now a Scottish team of researchers have made a breakthrough discovery. They identified 102 independent variants, 269 genes and 15 gene sets associated with depression.

The research team, led by Prof Andrew McIntosh of the University of Edinburgh, Centre for Clinical Brain Sciences, looked at the DNA and health records of more than two million people. The sample size included 807,553 individuals (246,363 cases and 561,190 controls) from the three largest genome-wide association studies of depression.

It was also discovered that there were significant interactions between the DRD2 gene and a class of drugs that includes typical and atypical antipsychotics. Interestingly, the results did not show any serotonin-linked genes which was surprising as most antidepressants alter the serotonergic system.

The analysis implicated mostly cortical brain regions in depression, in particular the frontal cortex (mostly responsible for complex decision making and personality) and the anterior cingulate cortex (emotion formation and processing, learning, and memory).

When the researchers examined depression with other behavioural and disease traits, more discoveries were made. There are links between depression and other mental health conditions (such as bipolar disorder and schizophrenia), depression and the age someone starts smoking as well as depression and the age at menopause.

“We looked to see, in around about two million people, if we could predict using genetics the people who developed depression from those who didn’t.”
— Prof McIntosh

A new hope for treating depression successfully

"We looked to see, in around about two million people, if we could predict using genetics the people who developed depression from those who didn't," Prof McIntosh said. We found that there were about a hundred or so changes in their DNA, in their genetic makeup, that made them more likely to develop the condition. It was the people that carried over 100 who were much more likely to develop the disorder in future."

Professor McIntosh also stated: "We hope the findings will help us understand why some people are more at risk of depression than others, and how we might help people living with depression more effectively in future.”