I saw a hair-raising talk on autism this evening, given by Prof. Manuel Casanova, MD, at the Louisville Skeptics' monthly Science Cafe. (Every month, they invite a scientist to give a talk at a local pub, O'Shea's in downtown Louisville.) Prof. Casanova is an internationally known researcher in neurosciences and autism at the University of Louisville; he is looking at "minicolumns" of neurons in the brains of people with autism (microscopic vertical columns of neurons in the neocortex). It turns out that these are more numerous and more tightly packed in the brains of people with autism, and Prof. Casanova explained that this allows cross-talk between the columns that would not occur in normal brains. This increases the excitability of the neurons, which normally would be suppressed by an inhibitory effect (he referred to a "shower curtain" that normally separates these minicolumns). This seems to make sense, given that one of the hallmarks of autism is a heightened sensitivity to stimuli; autistic people often find touch, various sounds or other sensations to be intensely uncomfortable.
Now this was interesting, but what made the talk hair-raising were statistics Prof. Casanova gave about the incidence of autism. It turns out that prior to 1990, about 1 in 2000 children had autism, but it increased to 1 in 220 by the year 2000, 1 in 150 by 2007, 1 in 110 by 2009 and 1 in 88 by 2011 (if I remember the numbers correctly). I was aware that autism has increased in recent years, but I was not aware of how much it has increased. I had the impression that much of the increase was due to an increased awareness of autism or a broadening of the diagnostic guidelines for autism, so that the actual incidence of autism hadn't really changed. But I was very disturbed when Prof. Casanova said that changes in diagnostic guidelines or increased surveillance only had a modest effect on the incidence in diagnosis of autism---the large increase in autism is real and only in the last two decades. Prof. Casanova explained that the increased numbers were produced in surveys carefully designed to follow the same populations using the same criteria for autism. He said that this is the great epidemic of our time; much larger than HIV/AIDS, and with a more profound impact on its patients. (Autism affects children; people with HIV typically are not affected until they reach adulthood, and HIV disease can be controlled with medications.)
Prof. Casanova said that the cause of the increase in autism is unknown but likely to be something in the environment: genetics cannot explain this rapid an increase in autism, and new research shows that environment is responsible for more than 50% of autism (something that surprised researchers). A member of the audience asked him if he had any suspicions or ideas as to what specific thing in the environment might be responsible for the increase in autism. He gave an interesting and surprising answer: ultrasound. He explained that ultrasound, often used to image a fetus in the womb, is not benign---it can cause damage, and it can stimulate cell growth. Ultrasound is used on broken bones to make them heal faster. However, he said that it would be impossible to epidemiologists to verify this because there are no uniform standards or practices for ultrasound. Prof. Casanova was asked about vaccines. He said mercury (used as a preservative in some vaccines) was not responsible for autism, but he suspected that allergic reactions or seizures caused by vaccines might cause autism; he mentioned cases where this appeared to happen. (It occurred to me that one argument against vaccines being responsible for autism is that in Denmark, they phased out the mercury preservative in vaccines but the rates of autism did not decrease. This would exonerate mercury, but not vaccines.)
One interesting thing Prof. Casanova said about autism is that people with autism have various symptoms that are similar to what people with migraine have. These can include dietary or gastrointestinal sensitivities and sensitivities to light and sound. I asked him if autism is more common in people with migraine; he said it was, and he also said the incidence of migraine has increased. Likewise, the incidence of attention deficit disorders has increased, inviting the suspicion that these are linked in some way or have the same underlying cause.