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About 10% of the population is left-handed, but 40% of those with schizophrenia are, according to a new study.

That suggests that handedness may be a window into biological markers that predict psychoses, say the researchers from the Yale Child Study Center. While the percentage of left-handers affected by mood disorders such as depression hovers around 11%, similar to the rate of left-handedness in the population, they are more highly represented among those suffering from psychotic disorders such as schizophrenia.

“In general, people with psychosis are those who have lost touch with reality in some way, through hallucinations, delusions, or false beliefs, and it is notable that this symptom constellation seems to correlate with being left-handed,” said study author Jadon Webb, a child and adolescent psychiatry fellow at the Yale Child Study Center.

The results, reported in the journal SAGE Open, emerged from a group of 107 people who were treated at an outpatient psychiatric clinic. Neurologists and behavior specialists recently proposed some interesting theories about why some mental health disorders skew toward lefties. Generally, the brain is asymmetrically divided when it comes to major skills and functions such as language and emotions. The right side of the brain, which left handers tend to engage more actively, is associated with mood and emotions, while the left side is typically home to language and personality-based characteristics. Brain imaging studies have found, however, that some left-handed people have more equal distribution of language skills on both sides of the brain. Such patterns may introduce more complexity into the way the brain processes language and incoming sensory information, and that can lead to higher rates of misconnections or failures in the neural network that then contribute to developmental issues or disorders.

If the work is validated, it could help researchers to find clues, or biomarkers among left-handers that could hint at the first signs of psychoses. These wouldn’t be used to brand left-handers as more likely to become psychotic, but could help to select out those who are at highest risk of developing the mental disorders and introduce them to treatments as early as possible.