Some of the disorders associated with brain development, such as dyslexia, schizophrenia, and hyperactivity disorder or ADHD, is also more common in left-handed people.
According to estimates by experts, about 10% of the world's people are lefties. Meanwhile, people who can use the left and right hands equally well with only 1% of the population.
What causes people to become left-handed part due to genetics. A research report published in 2009 in the journal Neuropsychologia estimates that about 25% of left-handedness is due to genetic causes.
Environmental factors in utero are also suspected to influence. Babies born to older mothers or low birth weight are more likely to become left-handed, also mothers who experienced stress during pregnancy are more likely to give birth to left-handed child.
In general, there is no IQ difference between normal and left-handed people significantly, but there is some evidence to show left-handed people are better at thinking broadly or develop new concepts.
Left-handed people also have an average salary of about 10% lower than the average person, according to research conducted by Harvard University.
Unfortunately, left-handedness appears to be related to the risk of a number of psychiatric and developmental disorders. Approximately 20% of people with schizophrenia is a lefty. The relationship between left-handedness with dyslexia, ADHD, and some other mood disorders has also been confirmed in several studies.
"The reason for this remains unclear. Usually the people who wear a lot of right hand, the left brain is more dominant. But this is not the same tendency in left-handed people. About 70% of people rely on left-handed left brain to process language, the most important brain functions , "said Metten Somers, a psychiatrist and researcher at the Utrecht University Medical Center in the Netherlands.
"30% of other left-handed people the right hemisphere of the brain showed a more dominant or evenly distributed. They are more prone to learning disorders and more at risk of brain disorders," added Dr. Somers.
The dominance of one hemisphere of the brain believed to be the scientists more efficiently. And there is no dominant hemisphere of the brain associated with mental disorders. Patients with schizophrenia, for example, they showed activation of brain hemispheres evenly (symmetrical) than normal people.
In a study in 2008, Alina Rodriguez, professor of psychology at the University Mid Ostersund in Sweden, found that both left-handed people or people who use the right and left hands equally well have trouble understanding the language of risk and have symptoms of ADHD as children.
In another study published in the journal Pediatrics, which involved nearly 8,000 children in Finland, Dr. Rodriguez found that children who use the right and left hands equally well associated with ADHD symptoms.
"One reason is known about left-handed people are, many studies that show that their brains work is hampered because their brains are different neural connections," said Robin Nusslock, professor of psychology at Northwestern University in Evanston, Illinois.
Scientists say that the left-handed and using right and left hand at breeding can be used as risk factors for psychiatric or developmental disorders.
The existence of these risk factors may encourage earlier examination of the disorder. However, the facts show that the left-handed people have many advantages in the field of sports.
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