February is a month of holidays in the United States. Ground Hog Day celebrates the hope for the end of the winter cold, Valentine’s Day is for those in love and President’s Day honors history-making presidents from the past. These occasions lift our spirits during the doldrums of winter weather.
Facebook posts from left-handers during the early weeks of 2018 suggest that left-handers are in a dark winter mood. Many of the posts ask about relationships between left-handedness and a variety of serious clinical conditions. Syndromes mentioned recently in connection with left-handedness are substance abuse, bipolar disorder, depression and chronic insomnia.
My previous blog post of January 18, 2018 indicated that there is little research evidence to support the idea that left-handers are particularly prone to substance abuse disorders. My February gift to left-handers is to assure them that there is no research evidence to suggest that left-handers are at higher risk for bipolar disorder, depression and insomnia. I read over 1,000 articles when writing my book Laterality: Exploring the enigma of left-handedness (Laterality) and I do not recall any substantive research limking left-handedness to bipolar disorder or insomnia. Researchers have explored a relationship between left-handedness and depression but the results, like those with substance abuse, are inconclusive concerning any association between the two. If research evidence does not support a relationship between left-handedness and various clinical conditions, why do these topics continue to pop up on Facebook? I can think of at least two reasons why these posts continue.
First, there is a historic connection between left-handedness and various disorders dating back to the 19th century. I recommend a recent book by Howard Kushner, a historian of science and a left-hander, titled On the other hand: Left hand, right brain, mental disorder, and history (On the other hand). This book details the long-standing bias among members of the scientific community that left-handedness is abnormal and, therefore, a risk factor for disorders and disabilities.
Second, members of the media will highlight a single research study especially if a reporter is left-handed and the research report mentions left-handedness. An isolated experimental result comes across news feeds and reporters disseminate the study results. This process gives the study a lot of attention often more than it deserves. Once this information hits the online universe it is difficult to convince left-handers to be skeptical about the results. A connection between left-handedness and bipolar disorder, for example, cannot be established with one study. Multiple studies over a period of years pointing to the same conclusion must verify that such a relationship exists. Researchers know that one year of scientific time is actually five years of real time. The progress of scientific verification is slow and it takes years to establish a definite connection between two complex variables such as left-handedness and a specific clinical condition.
A reporter called me to ask me to comment on a recent study linking left-handedness to schizophrenia. She told me that she is left-handed and she is worried about this possible connection. I told her that the research literature suggests that schizophrenics may have higher rates of inconsistent handedness but not necessarily higher rates of left-handedness. However, I asked her for the reference so I could read the study myself. As I suspected, the research report in question used a potentially unreliable measure of handedness and the connection to left-handedness was weak. Nevertheless, the media release based on the study emphasized what reporters thought to be the newsworthy aspect of the study…should left-handers worry about becoming schizophrenic? The answer is “no” and certainly not based on the results of one relatively weak scientific report. Attention left-handers!…keep this example in mind when you read Facebook, Twitter and other online sources connecting left-handedness to various disorders. Your concerns about your left-handedness should be guided by science and not the latest report on Buzzfeed or the HuffPost.