A new large-scale study of depression, analysing more than 620,000 individuals, has found that there is no single gene for the disorder, conflicting with past theories suggesting that a small selection of genes were responsible for the disease and potentially striking a blow to clinical agencies who hoped to create diagnostic tools and treatments for the faulty genes.

For at least 20 years a number of scientists have believed disorders such as anxiety and depression were caused by malfunctioning cell transport systems in the brain. The cause of these malfunctions was historically attributed to genes which regulate the uptake of neurotransmitters such as serotonin.

The researchers scanned through commercial and clinical genetic databases, such as those of 23andMe and the UK biobank, amassing a sample of genomes for hundreds of thousands of individuals and testing for the 18 most likely genetic candidates which have previously been believed to link closely to depression.

They took into account a number of measures of mood disturbance, as well as the potential for variations requiring an environmental trigger, such as socioeconomic adversity. They found no strong correlations.

The scientists made clear that depression and other mental health disorders could still be heritable, but that they are most likely influenced by a large number of variants, each with some level of effect.

5/4: Edited to remove suggestion study “debunked past hypotheses”.