It has been hypothesized that inconsistent cerebral dominance is related to immune disorders and the high prevalence of autoimmune diseases have been found in the left-handed individuals.
In the method, the Edinburgh Handedness Inventory was used to evaluate 313 atopic patients’ left-and right-handedness. The results from atopic patients were compared to 350 control individuals with same age and sex. It was found that more left-handed individuals were atopic patients.
As a result of this experiment, the number of left-handed individuals was higher among atopic group than non-atopic group. Therefore, it was concluded that there was an association between left-handedness and allergic diseases like rhinitis, asthma, eczema and urticaria.
Its mentioned in the article that incidence of left-handedness was found to be more common in males than females. Geschwind and Behan proposed a theory to further explain male left-handedness. During male fetal development testosterone production decreases the development of the left hemisphere, mostly the language region. In addition, they proposed that increased levels of testosterone could interfere with the development of immune system by suppressing fetal thymic growth. As a result of defect thymocyte development, thymus cannot properly go through the negative selection process, which can lead to autoimmune diseases.
Although the findings of this study supported the hypothesis, I think more research is needed to validate this study with many more subjects.
Jocelyn, Smith. University of York, Department of Psychology, Heslington, York YOl SDD, U.K. http://www.sciencedirect.com/science
I managed to find a bit more research on this topic. A small study of 27 left-handed and 37 right handed males showed that the left-handed cohort had significantly lower levels of total T-cells, T helpers, and HLA-Dr (MHC-II) expressing APCs. Other research has shown these cell types are decreased in patients with epilepsy who had a resection of the language-dominant portion of their brains, and increased in patients with non-dominant resections. They propose that different hemispheres of the brain regulate the immune systems via different pathways, causing functional asymmetry of the immune system. If there is a decrease in the development one hemisphere, the corresponding immune components will not develop properly, leading to autoimmunity.
ReplyDeleteThis post caught my eye because I live with anecdotal evidence: my left-handed roomate has bad eczema. But unlike the study cohort, my roomate is a girl. This blog has mentioned that high estrogen levels may be responsible for female susceptibility to autoimmune diseases, including allergy. Does anybody know whether increased testosterone in men could have the same developmental effects as increased estrogen in women?
Lengen et al. Brain and Cognition, Volume 69, Issue 1, February 2009, Pages 188-193
Being that autoimmune diseases are more prevalent in females than in males and that left-handedness is more prevalent in males than in females, if it were found that the number of left-handed individuals was higher among the atopic group than the non-atopic group, I am curious to know the percentage of males vs females in those groups as well as the percentage of left vs right handers.
ReplyDeleteExtremely interesting blog that caught my eye right away being that I am left handed!! And my interest grew even more as I have suffered from eczema and have had extremely sensitive skin since the age of 2. So sensitive where as a child I had to take oat meal baths and now I can only use fragrance free skin products. I looked further into atopic dermatitis I found an article that listed the hands, feet, ankles, wrists, face and eyelids as common places for atopic dermatitis. I personally have had a skin issue (eczema etc.) in all of these areas and mostly in the crooks of my elbows as a child. Although there definitely needs to be more research in the area I find the research very believable. Like "KellyG" mentioned, I am curious to see more research about the gender factor. Also, there is no definite research that shows Multiple Sclerosis as being caused by genetics. Yet there is speculation, and I wonder about possible genetic predispositions to immune disorders? My mother suffers from MS and I am curious as to whether maybe genetics have played a role in her MS along with myself being atopic and left-handed and the link between all of those things??
ReplyDeleteWhile this is an interesting association, there are relatively few studies that have looked at this, most being in the late 80’s, one being cited in the post, Coren 1994, and the most recent I found being Morfit and Weekes in 2001. These two replicated studies did not show a significance difference between handedness and allergic disease in a direct comparison, but did show a difference when the analysis was broken down more. The limited number of publications since the initial hypothesis suggests an inability of others to replicate the results. There are also the discrepancies already mentioned, such as a higher prevalence of autoimmune disorders in females. Lupus, for example, is biased 10 to 1, females over males. So, for the time being, I believe it is a fun coincidence.
ReplyDeleteI like this post a lot. Many studies do not look into fetal stages as a reason for these diseases but it would be where I think most of these disease originate at. There is so much that can go wrong in the womb when everything is being built up. Especially since a fetus does not have an immune system set up already. Of course it is protected for the most part but hormones make sense to have big repercussions because they are supposed to be there. It would be very interesting to do even more research on what other affects these higher levels of testosterone and estrogen have on the growing fetus.
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