The Connection Between Left-Handedness and Schizophrenia

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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.

13 comments
VeniceL
VeniceL

"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."

This doesn't seem to make sense. Surely you mean the percentage of those with mood disorders who are left handed is around 11%?

aliberaldoseofskepticism
aliberaldoseofskepticism

Wonderful. Now they're going to convince everyone mental illness is something sinister.

Alternately, I saw a movie about a dude who thought he could see the future and move objects with his mind. He was a lefty too. The movie was called The Empire Strikes Back.

TomHennessy
TomHennessy

A compilation of three studies finds schizophrenia and bi-polar to be linked, and coincidentally, left-handedness is found in more than fifty percent of those with bi-polar disorder.

"Common biology shared in schizophrenia and bipolar disorder"

"Left-handedness in a sample of nine patients with borderline personality disorder" "5 of 9 patients were reported to use the left hand"

sewmilligan
sewmilligan

The reports of left-handed people are out of date.  There is about 28 percent of the population that are lefties.  No there aren't : Yes, there are.  No there aren't.  Yes, there are.  Are too. Are not....  You're crazy.... No, YOU"RE crazy. No you're the crazy one.

Mykeljon
Mykeljon

Oh Tom, poor Tom! Talk about adding 2+2 and getting 5. While there may be some truth to the Canadian study, there is no attempt by that study to link homosexuality and schizophrenia. There are schizophrenics who are homosexual and there are homosexuals who are schizophrenic but there is no evidence to link them in any cause and effect relationship according to a study published in the American Journal of Psychiatry. To say that one is thought to be the other makes as much sense as to say that homosexuality is a form of migraine headache.

maxperfect
maxperfect

"There is no doubt that the actual methods used to analyze handedness influence the results, and indeed, studies that attempted to measure left-handedness versus a more inclusive mixed-handedness often produce different results (Dragovic & Hammond, 2005)."   The left-handed label is too general and imprecise and I believe misleading.  If you are not going to differentiate between left-handedness and mixed-handedness, then the next best label to use is "non-right handed".  A pure left-hand subject has brain functionality distributed asymmetrically like a right handed subject. The break through will come from discovering why mixed-handed brains are not asymmetric like right and pure left-handed brains. I wait for that day.

TomHennessy
TomHennessy

You may think if someone is prone to left-handedness is not prone to be psychotic but this article says left-handedness is related to being prone to psychosis. I simply pointed out that previous to this article, a book was written, 'The Bearded Lady Disease' in which the author has stated homosexuality and schizophrenia are closely linked. Schizophrenia is psychosis. So , I simply point out the coincidence of historic documents saying homosexuality is linked to psychosis and this article which coincidentally says left-handed people, who are prone to homosexuality, also manifest psychosis. Coincidence, or simply good simple science research? I don't believe in a lot of coincidences.