It is not just about genetics
Scientists are not really sure why people are left-handed, but it appears that about 25 percent of it is because of genetics. That, however, is not the only reason. Left-handedness does not really run in families just as much as other traits like height and intelligence do. In fact, even identical twins may turn out to have different dominant hands.
Being left-handed can put you more at risk of certain diseases
According to a 2010study published in the journal Pediatrics, being left-handed was associated with an increase in risk of dyslexia, certain mood disorders and ADHD. While scientists are not really sure why this happens, they do think that it is because of the way the brain is wired. Most lefties and righties depend on the left hemisphere of the brain. About 30 percent of left-handed people tend to either be partial to the right hemisphere or not have a dominant hemisphere. While lefties may be at a higher risk of certain diseases, they are lucky to not have other common diseases such as ulcers, arthritis, etc.
They have high risk of psychosis
Several studies done in the past have found that people suffering from psychosis tend to have a 20 percent more possibility of being left-handed. Researchers at the Yale University in New Haven, Connecticut and University of Texas Southwestern Center in Dallas looked at 107 patients at outpatient psychiatric clinics. People who had mood disorders tended to have 11 percent chances of being left-handed. Researchers thus theorize that brain does play an important role.
The brain doesn’t work all that differently
It is said that most right-handed people use the left hemisphere of their brains. This, however, does not mean that left-handed people use the right hemisphere. Almost 98 percent of right-handers use the left side of their brain or process language using the left side of their brain. Gina Grimshaw, PhD, director of the Cognitive and Affective Neuroscience Laboratory at Victoria University of Wellington in New Zealand said that most left-handers do not differ from right-handers in an obvious way.
Your mother may have had stress during pregnancy
A British study found that fetuses of super-stressed pregnant women tended to touch their faces with their left hand more than the right. This, the study suggests, could be the first signs of a left-handed child. Another Swedish study done in the year 2008 of moms and their 5-year-old children found that women who were stressed or depressed while they were pregnant tended to be highly likely to have kids that were left-handed.