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Autism has gone from being a mental disorder to an absolute fad. NASCAR has run races named after it. It has its own “spectrum” for differential diagnosis. Movie stars and athletes brag about their children’s autism. People with some condition in the “spectrum” write books bragging on themselves. It even has its celebrity cranks and medical quackery. When did autism get promoted from an unhappy malfunction of the brain to something special? Or is it, like the pink stuff for breast cancer, simply a result of aggressive and successful marketing? Does any of that marketing do anything for the people with autism and their families? Or, for that matter, further research into the condition with an eye to curing or at least improving it? —Your retired reference-librarian fan, Kathleen, aka Bookworm

Nothing like a good rant, eh, Kathleen? But be careful. If you start going on obsessively about something long after everybody else has lost interest, someone’s going to diagnose you as autistic.

More precisely, they may claim you have Asperger’s syndrome, one of the autism spectrum disorders (ASDs) you refer to. Those with the syndrome, named after Hans Asperger, the Austrian pediatrician who characterized it in 1944, focus obsessively and lack social skills or empathy. At the same time—and here we see why this condition has become fashionable—often they also have above-average intelligence and become wildly successful due to their powers of concentration and willingness to trample everybody else.

One guy famously said to have a touch of Asperger’s is Facebook founder Mark Zuckerberg, whose flat affect and general geekiness were caricatured in The Social Network. Other tech moguls supposedly displaying the signs include Craigslist founder Craig Newman, Bram Cohen of BitTorrent, and Microsoft’s Bill Gates.

You may say: we should all be such mental cases.

Just my point. If a so-called mental disorder is defined so broadly that any number of self-made billionaires are believed to have it, the diagnosis is useless and needs to be rethought.

Some background. Autism was once believed to be rare, affecting no more than one in 2,000. There was no mistaking those who had it: they were severely withdrawn, incapable of normal conversation or interaction, and often exhibited oddball, sometimes violent behavior or fixations.

Starting in the mid-20th century, though, some psychiatrists began defining autism more broadly to include children with serious psychosocial disorders but more or less normal language skills. This culminated in the inclusion of Asperger’s disorder in the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), published in 1994.

In a rueful 2011 essay, Allen Frances, the psychiatry professor who chaired the DSM-IV task force, said he and his colleagues knew that once Asperger’s was declared an official mental illness, diagnoses of autistic disorders would rise sharply—to one in 1,000, maybe even one in 500.

Little did they know. ASD assessment is subjective, based on things like lack of eye contact, hand flapping, and poor language skills—there’s no physical test or scan. Clinicians began seeing ASDs everywhere. Today the Centers for Disease Control estimates about one in 88 people has an ASD. A South Korean study claims the rate in that country is one in 38, nearly 3 percent of the population.

Whoa, said alarmed skeptics. The point of declaring something a disorder is to identify those who need help, not sort out future computer science majors. They got the diagnostic criteria for Asperger’s syndrome and other ASDs tightened in DSM-5, published last year. It’s thought 10 to 40 percent of those previously assessed with an ASD will no longer qualify.

We’ll see how that works out, but a lot of damage has already been done. To cite an obvious case in point: With ASDs seemingly epidemic, people looked for something to blame. In 1998 a team led by British physician Andrew Wakefield published an article in the medical journal Lancet purporting to link ASDs to MMR (measles-mumps-rubella) vaccine. TV personality Jenny McCarthy made headlines for years claiming not only that her son’s autism was caused by vaccinations, but that she’d successfully treated it with vitamins and diet. Wakefield’s article was ultimately discredited and retracted, but not before the MMR vaccination rate in the UK had dropped to 80 percent.

Autism advocates and parents of kids with honest-to-God cases of the disorder may say: OK, maybe ASDs have been overdiagnosed. So what? There’s strength in numbers, and the publicity has certainly raised autism awareness. The answer to that is: yes, but at the cost of obscuring the actual condition.

On the one hand you’ve got people thinking Asperger’s syndrome is the mark of a future tech genius and thus nothing to worry about; on the other hand, if there actually were an environmental cause of autism, with so many false positives being reported we’d never know. The biggest favor activists could do for the objects of their benevolence is to make people understand: here are the signs you’ve got an autism spectrum disorder, and, equally important, here are the signs you don’t. —Cecil Adams