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Depression and bipolar disorder can turn the life of a young person upside down and the onset of these disorders can come without warning. Yet, science can make it predictable.

Researchers at Dalhousie University have found that a genetic test can predict a person's probability of developing depression or bipolar disorder with far greater accuracy than other indicators.

In a new study published today in JAMA Open Network, they report that eight different polygenic scores are linked to someone's likelihood of developing major depression or bipolar disorder. Polygenic scores bring together thousands of genetic variants across the person's genome. Each of these variants may have a weak link with the risk of a disorder, but when thousands of these variants are collected into polygenic scores, the link becomes stronger.

Kate Freeman, a Ph.D. student in Medical Neuroscience at Dalhousie, discovered that polygenic scores indexing a variety of human characteristics related to mental health, like self-regulation and a tendency to addictive behaviours, all contribute to the risk of depression and bipolar disorder.

Previous research found that the onset of depression of bipolar disorder is more likely in young people whose relatives developed these disorders and in those who had earlier, more minor mental health problems like anxiety. Freeman confirmed these relationships in a sample of more than 1,000 young people. She also found that multiple polygenic scores helped forecast the risk of depression or bipolar disorder with greater accuracy than family history or childhood mental health problems alone.

The research found that polygenic scores for attention-deficit/hyperactivity disorder (ADHD), self-regulation and the tendency to addictive behaviours were more strongly related to the risk of bipolar disorder than to the risk of depression. In the future, these predictors may be used to decide between antidepressants and mood stabilizers as the initial treatment option. The researchers caution that the prediction is not yet ready for clinical use and requires more robust replication before it can be implemented in clinical practice.

Freeman and co-author Dr. Rudolf Uher, a professor in Dal's Department of Psychiatry, are available to discuss the findings, how risk prediction may help prevent the illness and if properly targeted to those at greater risk, could also help people get the proper treatment earlier.

The project was supported by a grant from Genome Atlantic.

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Media contact:

Alison Auld
Senior Research Reporter
Dalhousie University
Cell: 1-902-220-0491
Email: alison.auld@dal.ca