[projectramo]

This would be amazing if it works.

The reason I say "if" and hedge my words is because the conventional wisdom is that autism is not a single disorder with a single underlying condition. It is a cluster of symptoms of varying intensity and it is (likely) caused by a host of underlying conditions.

Two children diagnosed with the disorder can have no overlapping symptoms.

If that is right, then the first step is to break it down into different kinds of conditions. (No eye contact is caused by X. Speech issues are caused by Y).

However, if this test can effectively pick apart one of the underlying conditions and its symptoms that would be a huge step forward. We could definitively say whether a child has this particular version of "autism".

After we tease apart a few more versions, the original condition will disappear and be subsumed by these other versions.

[gowld]

I suspect the reason autism has such a constellation of symptoms isnot because the cause is complex, but because the environment (human brain and body) is complex. Imagine there was "cardboard box spectrum disorder", caused by keeping a child in a 4x4-ft box for their first 5 years. They'd develop a host of comorbid symptoms, in varying intensities, based on how the child developed coping mechanisms and workarounds to it's confinement, even though the actual cause is quite simple.

For autism, the "cardboard box" is something to due with the pattern of connections in the developing brain, and pattern has wide ranging impacts on many brain functions, which then influence physical functions , which cause feedback loops back to and inside the brain.

[InclinedPlane]

Case in point: girls and boys are diagnosed with autism at wildly different rates. But how much of this is due to actual differences in the incidence of autism versus the differences in the way girls and boys are socialized resulting in different appearances of symptoms?

This is true of many behavioral and cognitive conditions. The symptoms and severity of things like schizophrenia vary significantly from culture to culture (in some cultures schizophrenics hear benign or even kind voices versus here in the western world where the voices tend to be harsh and violent).

[projectramo]

Good point. However, this example could go either way.

Suppose everything you said is true, but in addition to all that, there is a set of symptoms caused by -- making this up -- endocrine disruptors in our drinking water. When pregnant women drink too much, they get some subset of symptoms from a set that overlaps 80% with the cardboard box symptoms.

Now we have two different causes for different symptoms. In addition, you can get the strange case where:

patient A, symptoms X, condition G

patient B, symptoms X, condition H

patient C, symptoms Y, condition G

patient D, symptoms Y, condition H

Although most of the time, condition G will have similar symptoms and condition H will have similar symptoms.

That's why it is so useful to have a marker.

[tejohnso]

> Two children diagnosed with the disorder can have no overlapping symptoms.

Is there a precedent for this with other disorders? Seems to me that if there are no overlapping symptoms, it should be a separate disorder. Even if it's just arbitrary naming like "Type X" as in diabetes.

[dwringer]

This might not be the most authoratative source, and I'm no medical expert, but this overview from Encyclopedia Britannica[1] nicely describes the diversity in how diseases are classified (I know we aren't using the term "disease" here but the concepts are presumably related in practice - I found this summary informative but welcome any informed corrections):

> The most widely used classifications of disease are (1) topographic, by bodily region or system, (2) anatomic, by organ or tissue, (3) physiological, by function or effect, (4) pathological, by the nature of the disease process, (5) etiologic (causal), (6) juristic, by speed of advent of death, (7) epidemiological, and (8) statistical. Any single disease may fall within several of these classifications.

[1] https://www.britannica.com/science/human-disease/Classificat...

[DanBC]

> Seems to me that if there are no overlapping symptoms,

The full name is "Autistic Spectrum Disorder", so the name hints that there's a range of stuff happening.

To be autistic someone has to have problems with social communication, problems making or maintaining friendships, and fixed and repetitive interests.

Some people also have other stuff on top. These things are common with autism, but are not needed for the dx.

Alexithymia (the ability to recognise emotion in yourself and others) is one example. It's far more common in autistic people, but you don't need it to be autistic. Between 50% and 55% of autistic people have alexythimia. Sensory sensitivities are another. There are a range of these things that are more common in autistic people, but aren't needed for the dx.

And there's a lot of co-morbidity too. People with autism are more likely to have depression or anxiety or OCD. These aren't part of autism, but it's complicated to untangle what's going on. Is someone social isolated because they're depressed, or autistic, or is it a bit of both?

When you start looking at these other things it makes sense that autism might be an umbrella diagnosis.

[gowld]

And it overlaps with the diagnostic "Pervasive Developmental Disorder" in case you thought ASD wasn't a big enough tent.

[cbhl]

In the DSM 5, "Pervasive Developmental Disorder - Not Otherwise Sepcified" (PDD-NOS) and others (Asperger Syndrome) got refactored into a single unified Autism definition.

[projectramo]

I think there are precedents.

It happens because there is so much overlap in most patients, and symptoms tend to occur in clusters.

General delays in motor skills and language skills are quite prevalent in many conditions. If you google videos of kids with autism, you will see varied abilities.

I am hesitant to go into more detail because this is an area that causes a great deal of anxiety for parents and discussions are often sensitive. One surefire way to annoy a parent and get into an argument is to claim their kid does or does not have a condition that differs from their own opinion. (And I can see why it would bother them).

[avip]

IBS, asthma, schizophrenia, ADHD, and the list goes on and on.

[thaumasiotes]

> Is there a precedent for this with other disorders? Seems to me that if there are no overlapping symptoms, it should be a separate disorder.

Yes, this is a pretty normal way of doing diagnoses.

Specifically, many disorders are diagnosed according to the template "the disorder is present if the patient presents any X out of this list of Y symptoms". As long as X is less than half of Y, it's possible for two patients to "have" the disorder without sharing any symptoms.

"Have" is in scare quotes because, obviously, this state of affairs is an artifact of the diagnostic criterion. However, it's also possible for e.g. two people to host infections of HIV without sharing any symptoms -- one may have AIDS while the other is asymptomatic.

[gowld]

Imagine a power set of 2^n possible symptoms, that tend to occur together. Would you create 2^n diagnoses?

[bjourne]

Most believe that there is a common source for varying diagnoses like ADD, ADHD and high functioning Autism. What that source is, is not yet known but people have hypothesized about certain genes causing it, or changes in the prenatal environment.

The disorder is much more prevalent in some families than others and even in some ethnic groups which strongly suggests that there are genes involved. One theory suggests that the genetic material came from when Homo Sapiens interbred with Neanderthals.

Autism is in some ways very similar to homosexuality. There is no one true test for it, but if you "look for the signs" you can "diagnose" even very young children. It implies that autism, like homosexuality, can't be cured. People with the disorder have to live with it and those around them have to adapt because they can't change themselves.

[gowld]

Even if diagnosis works perfectly, a brain scan tells you almost nothing about how to respond. The one benefit is to focus early intervention efforts on parents who will likely need ASD parenting skills in their child's next few years.