An article published in Reader’s Digest1 suggests you are at a greater risk for certain negative health and life outcomes if you are left-handed, including accidents, certain mental and physical problems and even early death.
While it’s obvious left-handers face challenges with respect to using everyday items like keyboards, notebooks, scissors and zippers, which are typically designed to favor right-handed users, does research support the notion left-handedness is actually dangerous to your health?
Factors That Influence Your Choice of Handedness
Handedness — your tendency to be more comfortable and skilled using one hand more than the other for tasks like dressing, throwing a ball or writing — is a complex matter. Although you may think it is determined solely by genetics, handedness is a complex trait influenced by multiple factors, such as chance, environment and genetics.
According to the U.S. National Institutes of Health (NIH),2 the development of handedness begins before birth and is influenced by genes, as well as both your right-left asymmetry and the right and left hemispheres of your brain. They state:3
“It was initially thought a single gene controlled handedness. However, more recent studies suggest multiple genes, perhaps up to 40, contribute to this trait. Each of these genes likely has a weak effect by itself, but together they play a significant role in establishing hand preference.
Studies suggest at least some of these genes help determine the overall right-left asymmetry of the body starting in the earliest stages of development.”
Science Daily highlights asymmetry as an important feature of your brain, noting the left side usually controls speech and language, while the right side controls emotion. They assert, “In left-handers this pattern is often reversed.
There is also evidence that asymmetry of the brain was an important feature during human evolution; the brains of our closest relatives, the apes, are more symmetrical than those of humans — and apes do not show a strong handedness.”4 Authors of a 2013 study published in the journal Neuroscience & Biobehavioral Reviews comment similarly:5
“Handedness is the single most studied aspect of human brain asymmetries. For long it has been thought to be a monogenic trait that can produce an asymmetrical shift of cerebral mechanisms, thereby producing right-handedness. Nevertheless, a single gene explaining a sufficient amount of phenotypic variance has not been identified.
The results of several recent studies using advanced molecular genetic techniques suggest that a multifactorial model taking into account both multiple genetic and environmental factors, as well as their interactions, might be better suited to explain the complex processes underlying the ontogenesis of handedness.”
Additionally, your prenatal environment and cultural influences are thought to play a role in determining which hand will dominate. In terms of prevalence, the NIH asserts 85 to 90 percent of the population in Western countries are right-handed.6 About 10 percent are left-handed and the remainder thought to be ambidextrous (able to use both hands equally well).
According to Clare Porac, Professor Emerita of psychology at Penn State University, the lowest rates of left-handedness, 4 to 6 percent, are found in Africa, Asia and South America.7
Genes Associated With Handedness
To date, researchers have identified a few of the genes thought to influence handedness. Two notable genes associated with handedness are:
• LRRTM1 (Leucine-rich repeat transmembrane neuronal 1) — This gene has been associated with an increased likelihood of left- or mixed-handed people also having schizophrenia or another neurological disorder.8,9
Authors of a 2001 meta-analysis featured in the British Journal of Psychiatry — involving 19 studies on handedness, 10 dichotic listening studies and 39 studies investigating anatomical asymmetry in schizophrenia — stated:10
“The prevalence of mixed- and left-handedness (‘nonright-handedness’) was significantly higher in patients with schizophrenia as compared to healthy controls, and also as compared to psychiatric controls. Strong evidence is provided for decreased cerebral lateralization in schizophrenia.”
• PCSK6 (proprotein convertase subtilisin/kexin type 6) — This gene has been linked to an increased chance of left-handedness being noted in people with dyslexia. Researchers involved with a 2011 study presented in Human Molecular Genetics commented:11
“These results provide molecular evidence that cerebral asymmetry and dyslexia are linked. Furthermore, PCSK6 is a protease that cleaves the left–right axis determining protein NODAL.
Functional studies of PCSK6 promise insights into mechanisms underlying cerebral lateralization and dyslexia.”
Potential Health Risks Thought to More Often Affect Left-Handers
Although being left-handed is not an exclusive factor in any health risk, there are a number of situations that have been linked to left-handedness. Research suggests left-handed people are at increased risk for:
• Accidents — A 1989 body of research published in the American Journal of Public Health12 focused on self-reported injuries and handedness in a group of nearly 1,900 Canadian college students.
Researchers found more left-handers (51 percent) reported having an injury requiring medical attention during the past two years than right-handers (36 percent). In addition, left-handed people were 85 percent more likely to be injured while driving a vehicle than right-handers.
• Breast cancer — While your diet, lifestyle and any number of environmental factors can influence your chances of developing breast cancer, a 2007 body of research presented in the British Journal of Cancer asserts left-handers are at greater risk than right-handers of being diagnosed with breast cancer, particularly after menopause.13
Based on surveys completed by 1,786 Australian women who were part of a larger multidecade health study, the scientists said, “Left-handedness may be an indicator of intrauterine exposure to estrogens, which may increase the risk of breast cancer.
Left-handers had higher risk of breast cancer than right-handers and the effect was greater for postmenopausal breast cancer.”14
• Earlier death — In a 1991 study featured in The New England Journal of Medicine,15 researchers analyzed death certificates and distributed questionnaires about handedness to the next of kin for 2,000 deceased individuals from two counties in southern California.
Based on 987 usable cases, they noted the mean age of death for right-handers was 75 years, as compared to just 66 years for left-handers. The study authors stated, “These results are consistent with predictions based on implied pathological factors and environmental interactions suggesting left-handers are at greater risk of death.”16
• Psychotic disorders — As mentioned, being left-handed could put you at increased risk for a psychotic illness. A 2013 study17 from Yale University observed the handedness of 107 patients diagnosed with a mood or psychotic disorder at a public outpatient psychiatric clinic in a low-income urban area.
Whereas the prevalence of mood disorders was 11 percent (a figure consistent with rates in the general population), they discovered 40 percent of the schizophrenic patients reported writing with their left hands.
Lead study author Dr. Jadon Webb, a psychiatrist at the Arapahoe Mental Health Center in Littleton, Colorado, and his team said, “Our results show a strikingly higher prevalence of left-handedness among patients presenting with psychotic disorders such as schizophrenia and schizoaffective disorder, compared with patients presenting with mood symptoms.”18
Other Ways Left-Handed People Differ From Those Who Are Right-Handed
Beyond the potential for increased risk of certain health-related outcomes, research suggests left-handed people are also prone to being affected differently than right-handers as it relates to alcohol, money and sleep, among other areas. Scientists suggest lefties:
• Drink alcohol more often — Earlier studies suggesting left-handed people were more prone to alcoholism than their right-handed peers have not stood the test of time.
“There is no evidence that handedness predicts risky drinking,” study lead Kevin Denny, associate professor of economics at University College Dublin in Ireland, told the British Psychological Society.
“Hence, the results do not support the idea that excess drinking may be a consequence either of atypical lateralization of the brain or due to the social stresses that arise from left-handers being a minority group.”19
That said, research highlighted in the British Journal of Health Psychology20 in 2011 involving 27,428 adults age 50 and older from 12 European countries indicated left-handers do, on average, drink more often than right-handers.
• Earn less money — A 2014 study, featured in the Journal of Economic Perspectives,21 suggests the salaries of left-handers were as much as 10 to 12 percent lower than their right-handed colleagues.
Study author and economist Joshua Goodman, Ph.D., associate professor of public policy at Harvard, noted the median income for left-handers in the U.S. was $1,300 a year less than the wages paid to right-handers.
Goodman stated: “A large fraction of this gap can be explained by observed differences in cognitive skills and emotional or behavioral problems. Lefties work in more manually intensive occupations than do righties, further suggesting their primary labor market disadvantage is cognitive rather than physical.”22
• Experience post-traumatic stress disorder (PTSD) — According to psychologists who showed volunteers an eight-minute clip from an intensely frightening movie, left-handed people were more likely than right-handers to exhibit fear.23
Their fear was notable in the sense they gave researchers more fragmented accounts of what they’d seen, an effect associated with PTSD.
Lead researcher Carolyn Choudhary, a lecturer in the psychology and sociology division at Queen Margaret University in Edinburgh, Scotland, presented the team’s findings at the British Psychology Society’s annual conference in 2011. She told The Telegraph:24
"The prevalence of [PTSD] is almost double in left-handers compared to right-handers. We used a portion of film from ‘Silence of the Lambs’ that we know elicits fear, so we could check the recalled account against the film.
People who were left-handed showed significantly more fragmentation in their memories and more repetition [than right-handers]. It appears these are tied to the way the brain makes memories during fearful experiences.”
• Sleep restlessly — Based on research involving 100 patients affected by periodic limb movement disorder (PLMD) — a repetitive cramping or jerking of your legs during sleep — the American College of Chest Physicians suggests left-handers are at greater risk than righties of developing the disorder.25
When the research was presented at their annual conference in 2011, the group noted 94 percent of left-handed patients had PLMD as compared to just 69 percent of right-handers — irrespective of variables such as age, race and sex.
Their findings indicate “left-handed people have significantly higher chances of having bilateral limb movements, indicating the potential for PLMD.”26
• Struggle in school — A 2009 Australian study published in the journal Demography,27 drawing on data collected from parents and teachers regarding 4,942 children ages 4 and 5 years old, suggests left-handed children perform less well academically than their right-handed peers.
The researchers noted the perceived “cognitive disadvantage” facing left-handers was not a result of demographics, socioeconomic status or behavior. About the study, they commented:28
“A broad range of skills were assessed, including vocabulary, reading, writing, copying, social development and gross and fine motor skills. Left- and mixed-handed children performed worse than right-handed children on nearly all of these measures.
Conversely, two measures showed no effect of hand preference: the PPVT [Peabody Picture Vocabulary Test] and expressive language skills. Both measures reflect a child’s vocabulary and ability to express ideas and do not require a written response.
Thus, it would appear that, despite being disadvantaged in most areas of cognitive achievement, left- and mixed-handers have the same ability for verbal expression as right-handers.”
It’s Not All Bad Being Left-Handed
In the event you’ve found this article to be somewhat depressing when it comes to the realities faced by left-handers, below are a few positives associated with being in the minority when it comes to being a lefty. Lefties are said to:29
• Be better at processing information at a fast rate — Research from Australia National University30 involving 100 people performing computer-based tasks showed left-handed people outperformed right-handers in processing large amounts of information at a fast rate.
Left-handers tend to use both sides of the brain more easily and therefore may perform better than right-handers at fast or complex tasks.
• Engage in right-brain activities more readily — Research published in the Journal of Mental and Nervous Disease asserts musicians, painters and writers are significantly more likely to be left-handed.31
The study authors said, “Creative people have been found to … be more likely to report an excess of nonright-handedness compared with controls … more widespread left hand use [was] reported by artists involved in the creative activities traditionally associated with the right [brain] hemisphere.” 32 Two areas mentioned were music and painting.
• More easily become ambidextrous — Given the reality most products and surroundings are geared to right-handed people, lefties are naturally challenged at a young age to use both hands, especially when it comes to putting on certain clothing with buttons and zippers, using notebooks, typing on keyboards and manipulating scissors.
• Stand out in a crowd — Given the tendency for their left-handedness to be easily noticeable, especially when eating, lefties often stand out in social situations. Because it’s common to exchange a handshake upon meeting someone for the first time, left-handedness can become a conversation starter.
Some Famous Lefties
Before ending, I can’t leave without mentioning that history is full of famous lefties whose names you will recognize right away, including eight U.S. presidents and many entertainers and entrepreneurs. Just a few of those famous lefties on a long list compiled by Time magazine include Barack Obama, Bill Clinton, Ronald Reagan, Oprah Winfrey, Bill Gates, Babe Ruth, Albert Einstein, Jimi Hendrix and Henry Ford.33
Source: mercola rss