Some disorders appear to be linked to being left-hand.

The New York Times - Tuesday, April 19, 1983 Jane E. Brody.

LEFT HANDED people, already burdened by minor inconveniences in a right-handed world and by a language full of such ego-deflating figures of speech as two left feet, out in left field and left-handed compliment, also seem to face an increased risk of certain disorders that can further impair the quality of their lives. A series of new studies show that left-handed people are more likely to suffer from learning disabilities, stuttering, migraine headaches and, according to the latest findings, autoimmune diseases, like ulcerative colitis, myasthenia gravis and celiac disease, in which the body attacks its own tissues.

The researchers emphasize, however, that their findings do not mean that left-handed people are at a biological disadvantage. Rather, they consider left-handedness an example of "biological diversity" that may be disadvantageous in some ways and beneficial in others. "Until you look at the full range of conditions and overall life expectancy among left-handed people, you cannot say whether it's a disadvantage," said Dr. Norman Geschwind, a leading researcher in the field. "It could be that left-handed people have only half the rate of lung cancer that right-handed people do." The studies by Dr. Geschwind and others suggest that the seemingly disparate array of conditions overrepresented among left-handed people may all stem from a variation in fetal brain development that is related to male sex, possibly the male sex hormone testosterone.

The result is that part of the left side of the brain grows more slowly than the right, leading to a change in the usual dominance patterns of the brain. At the same time, testosterone has been shown to interfere with the development of the immune system before and after birth. The job of this system is to recognize and protect the "self" against invasion by foreign organisms and tissues. "I think left-handedness is only a marker of what I call anomalous brain dominance." Dr. Geschwind said in an interview. Previous studies of left-handers have revealed such traits as better spatial relations, more emotional expressivity on the left side of the face, greater recovery of speech function following a brain injury, as well as a greater tendency toward cigarette smoking and alcohol abuse.

Left-handers have a decided advantage in certain sports activities, especially tennis and baseball. Although left-handedness had previously been associated with learning disorders and certain other problems, the possible biological significance of the connections had been unappreciated. In fact, the high incidence of the learning disability dyslexia among left-handed people had often been attributed to attempts by parents and teachers to force them to use their right hands. For example, the late Nelson Rockefeller, a dyslexic who tended to read and write words backwards, was a lefty whose father had tried unrelentingly but unsuccessfully to convert him to a righty. The new finding of a greatly increased risk of autoimmune disease among those who are strongly left-handed grew out of a chance observation by Dr. Geschwind, a neurologist at Harvard Medical School and Beth Israel Hospital in Boston. At a meeting of dyslexia researchers, Dr. Geschwind noticed that when people described their family histories, there appeared to be a disproportionate number of patients with autoimmune diseases among those with dyslexia and their families.

But Dr. Geschwind is quick to note that his finding was not merely serendipitous. Quoting the 19th-century scientist Louis Pasteur, he says: "In the fields of observation, chance favors the prepared mind." Dr. Geschwind's mind was prepared to look at the full spectrum of autoimmune disorders among left-handed people and among dyslexics on the theory that a genetic predisposition to a condition may be expressed differently in different people.

Studied Left-Handers' Problems.

Pengalaman membesarkan dan Mendidik Anak Kidal (Left handed). Anak saya yang kedua (Dr Suhaida Hanis) adalah kidal atau left handed...... terdapat kebenaran terhadap tulisan di atas. Amat jarang profession doktor perubatan yang kidal. Orang kidal biasanya tidak pandai sains sebab berfikir guna otak kanan... Selain itu, semasa kecil dia selalu sakit (terutama demam panas) sebab sistem imunisasi badan yang lemah. Pengalaman mendidik Dr Anis semasa kecil yang memang pada mulanya lembab amat mencabar sekali .... terutama bagi merealisasikan cita-cita sejak kecil untuk menjadi doktor perubatan...