Does Being Left-Handed Increase Your Risk Of Cancer? Here's What We Know

The world is designed to cater to right-handed people. Scissors don't work if you try them left-handed. Fixed desks in large lecture halls typically will be on the right. Ever noticed that older credit card machines had you swipe on the right side? Even though about 10% of the population is left-handed, researchers are still stumped as to why some favor their left hands. Some believe that handedness is a combination of a child's developmental process and as many as 40 genes, according to MedlinePlus.

While there are many myths surrounding left-handedness, such as higher creativity or intelligence, there are some scientific studies that suggest health differences between right and left-handers. An often-cited 2007 article in the British Journal of Cancer suggested that left-handedness may be linked to an increased risk of breast cancer. In particular, left-handed post-menopausal women were 2.5 times more likely to develop breast cancer than right-handed women after menopause. However, research linking left-handedness and cancer has been subject to debate.

A 2007 article in Epidemiology followed more than 12,000 Dutch women for 13 years. During that time, 252 women passed away. The researchers compared the mortality rates between left-handers and right-handers and found that left-handers had a 70% higher risk of dying from cancer and twice the risk of dying from breast cancer. They were also four times more likely to die from colorectal cancer. The researchers said that the research findings were limited by the small number of people who died during the study.

A 2007 commentary in Epidemiology criticized much of the research on left-handedness. The author wrote, "At this point, I should disclose that I am left-handed, and having successfully dodged a number of disorders, I doubt that my left hand is prematurely pulling me toward my grave. However, I am not alone in thinking that the literature on handedness suffers from a number of ills, irrespective of the putative illnesses suffered by left-handers."

The confusion of the research on the link between breast cancer and left-handedness was enough for Susan G. Komen to consider it to be a myth. The organization noted that several other studies have found left-handed people don't have an increased risk for breast cancer.

A 2003 article in Cancer Epidemiology, Biomarkers & Prevention looked at the connection between handedness (being left or right-handed) and the risk of developing brain tumors. The results suggested that individuals who identified as left-handed or ambidextrous had a lower risk of brain tumors compared to those who identified as right-handed. The reduced risk was observed in both men and women, as well as for tumors on the left or right side of the brain. The researchers cautioned that these findings need further confirmation.

McGill believes that the research showing a connection between left-handedness and health could be attributed to publication bias, which says that positive findings are more likely to be published, leaving readers uncertain about the existence of unpublished studies that find no connection. Some researchers might put left-handedness as an extra question in a survey that might be unrelated to handedness, and if a link is found, they'd publish it. If not, it's not mentioned in the study. It also pointed to the shock value of some of the research findings on left-handedness that often gets publicized in the media. This often perpetuates the myths and misunderstandings regarding research.