While some research suggests left-handed people have an increased risk of certain health conditions, most of the studies suggesting this were very small or have quality concerns.

About 10 percent of the population is left-handed. The rest are right-handed, and there are also about 1 percent who are ambidextrous, which means they have no dominant hand.

Not only are lefties outnumbered about 9 to 1 by righties, there are health risks that appear to be greater for left handers, too.

A 2007 study published in the British Journal of Cancer examined hand preference and cancer risk. The study suggested that women with a dominant left hand have a higher risk of being diagnosed with breast cancer than women with a dominant right hand.

The risk difference is more pronounced for women who have experienced menopause.

However, researchers noted the study only looked at a very small population of women, and there may have been other variables that affected the results. The study concluded further investigation is needed.

A 2011 study from the American College of Chest Physicians suggested that left handers have significantly higher chances of developing periodic limb movement disorder (PLMD).

This disorder is characterized by involuntary, repetitive limb movements that happen while you sleep, resulting in disrupted sleep cycles.

A 2013 Yale University study focused on the left and right handedness of outpatients in a community mental health facility.

The researchers found that 11 percent of the patients studied with mood disorders, such as depression and bipolar disorder, were left-handed. This is similar to the percentage of the general population, so there was not an increase in mood disorders in those who were left-handed.

However, when studying patients with psychotic disorders, such as schizophrenia and schizoaffective disorder, 40 percent of the patients reported writing with their left hand. This was much higher than what was found in the control group.

A 2007 study published in the Journal of Traumatic Stress screened a small sample of nearly 600 people for post-traumatic stress disorder (PTSD).

The group of 51 people who met the criteria for a possible PTSD diagnosis contained significantly more left handers. Left-handed people also had significantly higher scores in arousal symptoms of PTSD.

The authors suggested the association with left handedness may be a robust finding in people with PTSD.

A 2011 study published in The British Journal of Health Psychology indicated that left handers reported consuming more alcohol than right handers. This study of 27,000 self-reporting participants discovered that left-handed people tended to drink more often than right-handed people.

However, in fine-tuning the data, the study concluded that left handers were not more likely to binge drink or become alcoholics. The numbers did not indicate a “reason to believe that it is associated with excessive alcohol consumption or risky drinking.”

It appears that left handers have other disadvantages when compared to right handers. Some of these disadvantages can, in some cases, be related to future healthcare issues and access.

According to a 2009 study published in Demography, left hand dominant children are liable not to perform as well academically as their right handed peers. In skills such as reading, writing, vocabulary, and social development, left handers scored lower.

The numbers did not substantially change when the study controlled for variables, such as parental involvement and socioeconomic status.

A 2014 Harvard study published in the Journal of Economic Perspectives suggested that left handers in comparison to right handers:

  • have more learning disabilities, such as dyslexia
  • have more behavior and emotional problems
  • complete less schooling
  • work in jobs that require less cognitive skill
  • have 10 to 12 percent lower annual earnings

Although left handers have some disadvantages from a health risk perspective, they also have some advantages:

  • A 2001 study of over 1.2 million people concluded that left handers did not have a health risk disadvantage for allergies and had lower rates of ulcers and arthritis.
  • According to a 2015 study, left-handed people recover from strokes and other brain related injuries faster than right-handed people.
  • A 2006 study suggested that left hand dominant people are faster than right hand dominant people at processing multiple stimuli.
  • A 2017 study published in Biology Letters indicated that left hand dominant athletes in certain sports have a much higher representation than they do in the general population. For example, while about 10 percent of the general population is left hand dominant, about 30 percent of the elite pitchers in baseball are lefties.

Lefties can also be proud of their representation in other areas, such as leadership: Four of the last eight U.S. presidents — Gerald Ford, George H. W. Bush, Bill Clinton, and Barack Obama — have been left-handed.

Although left hand dominant people represent only about 10 percent of the population, they appear to have higher health risks for certain conditions, including:

  • breast cancer
  • periodic limb movement disorder
  • psychotic disorders

Left handers also appear to be at an advantage for certain conditions including:

  • arthritis
  • ulcers
  • stroke recovery