Large-scale DNA study links depression with smoking

Hundreds of genes have been newly linked to depression, shedding light on the origins of the condition and highlighting personality types that could be at risk.

The international study, involving more than two million people, is the largest of its kind.

It could inform treatments for the condition, which affects one in five people in Ireland and is the leading cause of disability worldwide.

Scientists led by the University of Edinburgh studied information pooled from three large datasets of anonymised health and DNA records and pinpointed 269 genes that were linked to depression.

They also used an innovative statistical method to identify sections of DNA that were common in people with depression and in those who adopted lifestyle behaviours such as smoking.

The findings suggest that depression could be a driving factor leading some people to smoke, but more research is needed to explain why, the team says.

Results also show that neuroticism — a tendency to be worried or fearful—– could lead people to become depressed, which could shed light on personality factors that put people at risk. The statistical approach — known as Mendelian randomisation — allows scientists to look at how a condition impacts on behaviour, while ruling out other influences such as age or income.

Experts say that the study reflects the importance of data science in understanding mental health.