What form of Autism is most common?

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Subject asks it all. I am wondering what form of autism is the most prevalent. Also, which side of the spectrum a majority of autistic fall on. Has there been any studies to determine this? I keep here people say LFA is more common, and others saying HFA is more common. Is there anything to back up these claims, or is it merely said people making up stats to defend their argument?

I recall a figure of either 5 or 0.5 people per 1000 have really severe autism, a.k.a classic autism. The overall incidence is much higher, I've seen a figure of 1 in a 60. The vast bulk of that is made up of people with non-classic autism. So I'd say HFA.

Surely it also depends on where one lives. It's genetic, so I should imagine it is more prevalent in certain populations.

Time to reveal ignorance. What do HFA and LFA stand for?

I've read somewhere that 60% of the autistic population have LFA

LFA=low-functioning autistic
HFA=high-functioning autistic

Sound somehow wrong and judgemental, those words...

This is further compounded by the fact that someone who is severely autistic can be high-functioning. Mild/moderate/severe/profound autism describes the symptoms, yet LF/MF/HF describes how well someone functions.

Some studies suggest PDD-NOS is more common than autism.

PDD-NOS is a synonym for 'you definately have autism, but we can't categorise you'. It's most common because it's very vague, and covers most of the population. Very few people aren't Autistic.

So what are all the categories, and what distinguishes them from each other (briefly)? I heard there are seven in the spectrum, plus Tourette's and ADHD which lie somewhere on the side, but I can't remember all the official Autism Spectrum Disorders.

Retts, Aspergers, Kanners (classic, right?) are all I can recall, and I don't even know what Retts is.

Then the fact that there's no single cause complicates things.

I don't think that there's any way to answer that, because less severe cases are unlikely to be diagnosed, and female cases are likely to be misdiagnosed. Since the line is pathology, it can be diagnosed if it's a problem, but lots of people have problems with the same issues but never get help, and even if they do, it may not be correctly diagnosed. Say someone with HFA/AS goes to see a therapist. They may be depressed an anxious because of their social problems. Most therapist won't recognize this, and will approach it as problems of mood and self-esteem. Also, I have a theory that the same symptoms that would be diagnosed in a man as AS are diagnosed in a woman as a personality disorder, particularly Borderline Personality Disorder. The outer features are very, very similar, it's the inner experience of the disorder that's completely different. It's a disorder diagnosed almost exclusively in women. It's also a diagnosis given mainly to "problem patients" that a professional just doesn't like.. people with unrecognized AS tend to be disliked by the very nature of inability to understand social cues.

So while I'm pretty sure that LFA is diagnosed more often than HFA or AS, I'm almost completely certain that the latter is simply under-diagnosed.

In the studies, when they refer to autism, they mean autistic disorder. They suggest PDD-NOS is more common than this.

Thanks, that helped me at Google. I found this:
http://www.yourlittleprofessor.com/spectrum.html

Infintile autism, classic autism, or what is otherwise known as LFA, represents only .5 of 1000 people. It is the LEAST common variety of autism. The vast majority fall in the High Functioning part of the spectrum, with AS, HFA and PDD-NOS as the primary diagnosises. The number of people with autism jumps to 1 in 150 with these three groups.

I have been at lectures and had conversations with doctors and therapists in the field, and they have confirmed this. The ONLY people who think the severe part of the spectrum represents the majority is the pro-cure set.

There's an epidemiology paper here: http://www.psychiatrist.com/supplenet/v66s10/v66s1001.pdf.

There's a bar chart on page 5 showing some prevalences. There are wide variations between studies.

Last edited by outlier on 19 Jun 2009, 5:38 pm, edited 1 time in total.