Genes linked to schizophrenia, bipolar disorder

The independent studies, each conducted by a consortium of about 200 scientists, also found significant genetic overlap between the debilitating mental disorders.

Schizophrenia patients typically hear voices that are not real, tend toward paranoia and suffer from disorganized speech and thinking. The condition is thought to affect about one percent of adults worldwide.

Previously known as manic depression, bipolar disorder is characterised by hard-to-control mood swings that veer back-and-forth between depression and euphoria, and afflicts a similar percentage of the population.

The biological profile of both conditions remain almost entirely unknown. Doctors seek to hold them in check with powerful drugs.

Scientists have long observed that each syndromes tends to run in families, suggesting a powerful inherited component.

But early hopes of finding a single-gene culprit swiftly faded, giving way to the realisation that -- to the extent DNA is at fault -- blame is probably spread across dozens, maybe even hundreds of DNA variants.