Bayesian Investor Blog

My understanding of Aspergers/autism (AS) and ADHD suggests to me that they can’t coexist in one personality. I keep coming across reports of people having both, and I’ve been trying to research whether those reports result from mistaken diagnoses or whether I’m missing something. I haven’t found any insightful discussion that addresses this directly. I’ve done some research on ADHD recently which clarified my ideas on this subject.

Both produce social problems due to unusual ways in which their attention works, and both involve unusually focused attention, which produce a good deal of overlap in symptoms. But there are many other features for which the two seem opposites.

ADHD – shifts attention easily and quickly in response to new stimuli
AS – slow to shift attention in response to stimuli

ADHD – seeks adrenaline rush from stimulating/risky situations
AS – avoids being overwhelmed by stimulating/risky situations

ADHD – often pays attention to multiple tasks at once
AS – finds multitasking unusually hard

From answers.com:

ADHD – makes inappropriate comments due to being impulsive but realizes afterward it was inappropriate

AS – makes inappropriate comments due to not knowing better and not understanding social conventions

ADHD – forgets details of daily routines

AS – follows daily routines rigidly

From another source:

Children with ADHD frequently break rules they understand, but defy and dislike. Children with Asperger’s Syndrome like rules, and break the ones they don’t understand. They are ever alert to injustice and unfairness and, unfortunately, these are invariably understood from their own nonnegotiable perspective. Children with ADHD are often oppositional in the service of seeking attention. Children with Asperger’s disorder are oppositional in the service of avoiding something that makes them anxious

With all these traits, there are wide variations in the degree to which anyone has them. But most of what I know suggests that people on one side of the AS/ADHD spectrum with regard to one of these traits are almost always on the same side with respect to the others, or else too close to the middle to classify.

Since many of these traits are poorly observed by those who diagnose them (you don’t observe peoples’ daily routines in a doctor’s office), it’s easy to imagine that widespread mistakes in diagnoses create a false impression that AS and ADHD coexist. Does anyone know of a good analysis that disagrees with my conclusion?

[Update 2010-11-15: I've gotten some feedback from people with some ADHD traits who don't clearly fit the pattern I've described. Maybe my analysis only works for one subtype of ADHD, or maybe things are too complex for any existing categories to work as well as I'd like.]

This paper reports that people with autistic spectrum symptoms are less biased by framing effects. Unfortunately, the researchers suggest that the increased rationality is connected to an inability to incorporate emotional cues into some decision making processes, so the rationality comes at a cost in social skills.

Some analysis of how these results fit in with the theory that autism is the opposite end of a spectrum from schizophrenia can be found here:

It seems that the schizophrenic is working on the basis of an internal model and is ignoring external feedback: thus his reliance on previous response.I propose that an opposite pattern would be observed in Autistics with Autistics showing no or less mutual information, as they have poor self-models; but greater cross-mutual information , as they would base their decisions more on external stimuli or feedback.

An unusual hypothesis about autism involves Genomic imprinting (”imbalances in the outcomes of intragenomic conflict between effects of maternally vs. paternally expressed genes.”).

It’s apparently somewhat well established that some regions of the brain are influenced more by paternal genes (the paternal brain), and some by maternally genes (the maternal brain).

The Imprinted Brain theory of autism says that autism results from the paternal brain being more developed, and the maternal brain being less developed, with an increased paternal brain causing Aspergers syndrome, and a reduced maternal brain causing more severe autism.

The father’s genes want the mother to invest more resources in a child than the mother’s genes do. Maternal genes have more desire for child to empathize with her and siblings to make childcare less costly. Paternal genes have more desire for competition between siblings over resources.

I had previously been impressed by a theory in the book Shadow Syndromes that involves a less developed cerebellum causing a slowness to shift one’s attention as a child, which makes one less likely to notice facial expressions. The Imprinted Brain theory can imply this (the cerebellum is one of the maternal brain areas which is underdeveloped).

The evidence is hard to summarize, but here’s an example:

autism increases with paternal (and maternal) age (Gillberg, 1980), and assisted reproduction via intracytoplasmic sperm injection (ICSI) may increase the risk for syndromes of dysregulated imprinting, including Angelman and Beckwith-Weideman (Paoloni-Giacobino & Chaillet, 2004; Waterland & Jirtle, 2004; Maher, 2005). Both paternal age and ICSI are expected to contribute to methylated-gene defects, which may include effects on brain-imprinted genes (Waterland & Jirtle, 2004; Malaspina et al., 2005).

I recommend reading the discussion section of the paper, which contains much more information than I can summarize.

The paper also mentions evidence that paranoid schizophrenia is an opposite of autism (involving a highly developed maternal brain) – schizophrenics are more likely than most people to notice/imagine that someone is looking at them (see (Mentalism and mechanism and The eyes have it).

Here is an apparently unrelated argument for schizophrenia and autism being opposites.