Saturday, November 21, 2009

8. Explaining the Gender Bias in ADHD

It is curious that the incidence of ADHD is much higher in boys than in girls. Some estimates claim that the ratio of boys to girls diagnosed with ADHD is as high as 10:1. In the context of a theory that ADHD is caused by fat insufficiency, what are the factors that might afford protection for girls?

First of all, the ratio of fat to muscle in girls is generally much higher than in boys. For the same body weight and size, a girl will have significantly more subcutaneous fat, as contrasted with a much higher muscle-to-fat ratio for a boy. This implies that the supply of bioavailable fats will be significantly higher for girls than for boys.

Secondly, and most importantly, the female hormone estrogen is a powerful weapon for increasing fat metabolism. Exactly how this is accomplished remains somewhat unclear, but it has been hypothesized that estrogen achieves this effect by stimulating an increase in both growth hormone and adrenaline. Growth hormone has been demonstrated to increase mobilization of fatty acids from fat tissue [30], and it is well known that adrenaline does this too [24]. Growth hormone also inhibits insulin production, and reduced insulin at the outset would greatly improve the odds of getting insulin levels sufficiently suppressed to allow fat mobilization.

Several investigators have studied gender differences in plasma free fatty acids in response to exercise, and have shown that females end up with significantly higher levels of fatty acids in the blood after an equivalent amount of exercise than do their male counterparts [2].

Thus, the extra fat cells, the enhanced mobilization of fat from these fat cells in general, and the enhanced effect of exercise on fat release all likely contribute to the significantly reduced likelihood of a girl succumbing to ADHD than a boy.


forrest said...

Gabor Mate's book on this describes a wide variety of ways in which the delayed development of emotional control [not suppression] & sustained interest called ADD can manifest. Hyperactivity isn't always involved; it sounded like females were more prone to handle this by simply suppressing their emotions, to comply with school demands but without engaging their interest. I remember one girl from my student-teaching days, who was able to read a pretty funny piece [James Thurber] but read it like a phone book, seemed likely [as I've heard commonly happens] to make it through school as if anesthetized for 20 years.

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