Monday, December 21, 2009

Autism Prevalence

A CDC report about autism has lead to some dramatic reactions. Here are some of my thoughts about this "1 in 100" "epidemic".

Summary, in case you want to skip the rest: Diagnosis got "better" for a while, but now I think we're overdiagnosing. There is really poor standardization in the medical field, and practically no oversight. Doctors refuse to let "bureaucrats" (epidemiologists, statisticians, and scientists, really) get in between them and their right to do whatever they feel like to their patients. New Jersey and Missouri have relatively high rates of ASD diagnoses because of nonstandard diagnosis practices. I expect the diagnosis rate to continue to increase, and that this is inefficient overall.

Firstly, remember that autism is not a disorder. There is a spectrum of severity of different features. To get an autism spectrum disorder (ASD) diagnosis, you don't need all the features, and they don't have to be severe. The primary feature involves impaired social interaction. Repetitive behaviors and sensory sensitivity are also common.

One big reason for the rise in the rate of autism diagnoses is that kids who would have otherwise been identified as mentally retarded are now being correctly classified. That is good because more helpful interventions can be assigned when diagnosis is accurate.

Unfortunately, another big reason for the rise is overdiagnosis. ASD is popular and famous. Neurotic parents whose kids aren't meeting expectations, who aren't the superstars the parents wanted, are looking for reasons and targets of blame and sources of hope. A lot of doctors just don't understand what they're doing, want to appease neurotic parents, practice defensive medicine, and benefit from making referrals to friends or businesses they have stakes in. The same nonsense that we see with ADHD and Bipolar diagnoses is happening with ASD. Little Billy likes to play by himself? ASD! Off to the occupational therapist! Little Billy has a slightly smaller vocabulary than his peers? ASD! Off to the speech therapist! Now, there are often cases in which some intervention would legitimately help a child, but interventions are expensive and different third-party payers have different diagnosis requirements for covering them. Well-meaning doctors commit a lot of insurance fraud, handing out inaccurate diagnoses in order to get a payer to pay for a useful intervention. This can be good for a client, but it is bad for our system. I generally see an enormous amount of money spent on small improvements.

The CDC report pertains to 8-year olds. There is generally a spike in diagnoses around age 8 because that is the transition to a developmental stage in which certain skills (reading and writing) are expected, as well as levels of self-regulation and interpersonal behavior. This is when school puts on more responsibility. Many learning disorders are suddenly noticed around this age. It makes sense for the CDC to use this age as it is likely to include cases caught late, though most autism should be recognized by age 3, when language is rapidly developing. A few teachers over the years increase the odds of recognizing problems.

What would be very interesting to look at is how many of these kids meet diagnostic criteria at age 12 or 18. There are a lot of reasons that kids develop skills and behaviors differently from each other, but a lot evens out the older they get. Many people carry around diagnoses like tattoos long after their natural developmental processes or interventions brought them into the normal range. All it takes is one doctor to use a label and a person who doesn't know better believes he's disabled for life, no matter what improvements are made. Anecdotally, I am familiar with a little girl who is almost three. She is quite a chatterbox now, but a doctor flagged her a year ago as having a low vocabulary. He offered the mother a referral to a therapist who would help the girl develop an average vocabulary for her age. Quite ridiculous and unnecessary and expensive. This was a doctor in New Jersey, by the way, which has the highest ASD rate in the country. Perhaps there is a medical culture in NJ that tends towards overdiagnosis. Perhaps their medical schools need to teach statistics better.

There is a lot of variance out there. People are different from each other. Every skill or characteristic of a person lies within a distribution. Half of people are below the average, and half above. There is a statistical term called "standard deviation" that describes how far from the average a person is relative to how widely people vary from each other in general. Most people are within 1 standard deviation of the average. There is precedent for saying that a person has a disorder when a characteristic of health or function is more than two standard deviations worse than average (a bit more than 2% of the population). Mental retardation is considered when a child's IQ is two standard deviations or more from the average. Many psychological tests flag problems when a person scores more than two standard deviations from the average on scales related to depression, anxiety, etc... But that alone should not be used to demark disorders or assign diagnoses. There has to be a convergence of information showing meaningful dysfunction.

Based on this precedent, we should not be surprised if the ASD diagnosis rate approaches 1 in 40. Kids who are socially awkward enough to rate as two standard deviations away from average on whatever metric someone makes up (there are a bunch of ASD symptom checklists out there, and they are not used well) would qualify for ASD. Asperger's and "high-functioning autism" are ballooning. We've gone past the point where formerly-mentally-retarded kids are being correctly identified with ASD, up to the point where formerly normal kids are being dragged into disorder land. They were probably called "weird" before, but is that something we need to fix? Is it really a problem?

I can't help but compare Asperger's to homosexuality. It was not long ago that homosexuality was considered a mental disorder. Now the legitimate medical community accepts homosexuals as healthy people who are just in a minority on a characteristic. We are surrounded by people who meet criteria for Asperger's, but they do well in academics, science, and technology. They are computer programmers and engineers and scientists and professors. Do we really need to say they are disordered because they're socially awkward and repetitive? Criteria C is redundant because criteria A necessarily involves social impairment. Are we really helping by imposing labels and interventions on these children?

Maybe. I don't know. I hope someone is recording a lot of data, and that there are enough "natural experiments" going on to eventually give us the answers. We definitely do need better standardization of diagnosis practices.

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