As concern over the spread of COVID-19 increases, attention is focused on the risk of infection associated with the presence of pre-existing conditions. Being over sixty-five or having a heart, lung or immuno-suppressive condition are pre-existing conditions that raise the probability of contracting a more virulent form of the virus. A theory that circulated in the early 1990’s argued that left-handedness is a pre-existing condition affecting health and well-being. The theory proposed that left-handers are alinormal. Left-handers may look like right-handers on the surface, but internally they are physiologically challenged in ways that make them more prone to illness and disease. As one might expect, this theory generated a lot of scientific attention and was quickly debunked when researchers failed to find any consistent relationship between left-handedness and various health conditions. However, one still finds Facebook posts from left-handers concerned about their disease susceptibility. These worries are remnants of this past history. Scientific theories may be discredited but some remain alive in the popular imagination.
My last blog post described a large internet study done in the Netherlands and published this year in 2020.¹ The study collected data from over 20,000 adults with more than half of the respondents being left-handed. In addition to the creativity results discussed in my previous blog, the researchers explored the relationship between handedness side and health variables. The authors asked the participants about their health history over a twelve month period. How many times they were sick, how many days they were sick and whether or not they suffered from allergies. The authors hypothesized that, if they found a difference between right- and left-handers, it would be in the direction of a health disadvantage for left-handers. Instead, they found the opposite. Left-handers had fewer health problems and were sick less frequently than right-handers. There was no relationship between handedness type and the presence of allergies.
This is good news for left-handers. Results from research with such a large sample that contains many left-handers contradicts the idea that left-handedness is a pre-existing risk condition for contracting everyday illnesses. Although the researchers found that left-handers had a health advantage, often results from large samples show statistical significance that does not translate into meaningful relevance for everyday life. For example, right-handers reported higher rates of illness and health problems when these were analyzed as individual variables. When the authors computed a composite score of the two responses, there was no relationship between this score and handedness type. It may be time to abandon the search for a connection between handedness and health.
¹The creativity myth, March 6, 2020.