I spent a decent amount working on ADHD diagnostics and unfortunately it sucks. To my knowledge, to this day, there isn’t a single reliable biomarker that identifies autism spectrum disorders. It’s usually correlation studies paired with questionnaires which for lack of better words can be described as “incidental” at best. Most z scored tests I know are also developed with small samples, a hundred participants with an outgroup of 20 would already be a LARGE sample. The standard ADHD questionnaire was validated on some 35 people.
There might be some hope in deep learning, particularly in observing eye movement components to deliver reliable biomarkers in the future, but I’m not so confident any time soon.
It’s dreadful and fascinating at the same time that defining and testing for ADS has been so elusive for so long…
From a molecular neuroscience perspective, for both ADHD and ASD (autism) you're unlikely to find any pure biomarkers as clean as a disease like huntingtons disease whose mechanism is clearly understood as extra CAG repeats on the HTT gene (a clean mendelian disorder). ADHD is defined by behavior/cognitive symptoms and most all behavior/cognitive diseases are multifactoral, which ADHD is. WES/WGS and GWAS has been done and for familial ADHD and unlike ASD there is mostly no clear monogenic mutation (a single gene that would explain the phenotype) [note monogenic mutations are usually a very small subset of cases but give scientists a look into what pathway/mechanism is causing a multifactoral disease]. Thus it is not for a lack of looking classically, and deficit is speculated to likely manifest as a neural circuit organization or synaptic issue (though the latter is more closely linked to ASD). This is currently impossible (basically) to measure in alive human brain as it requires nanoscopic imaging, note how challenging the fly map was (incomplete IMO as well).
There’s a doctor who goes by Russell Barkley, PhD on his popular YouTube channel and claims to be able to brainscan for ADHD with certainty. Is his claim legitimate?
ADHD also evolutionary advantages, so there is unlikely to be a single gene that encodes for it.
Evo-psych is impossible to falsify.
What are they? Are there papers on this?
There are only papers which suggest this could be true, none that conclusively prove it. That I’m aware of.
There are some cool studies done where people with a without ADHD are tasked to forage berries. The people with ADHD do better and adhere to foraging patterns which existing theories suggest would be more optimal.
A lot of the studies like that indicate the individual with the condition might benefit more from ADHD than the group they’re in, but I’m not sure that studies have explored group benefits very much.
There’s an often cited paper in which nomadic men who carry a certain ADHD-related allele (DRD4-7R, a dopamine reception variant with ADHD traits and novelty seeking) tend to have better nutritional status. I can’t recall much about it or how high quality it is.
I’ve always thought, it’s not absurd to think there different development routes which the brain takes depending on the environment it develops in.
With your foraging example, it does make me think ADHD is a small group/individual optimisation. Prioritising high vigilance and individual productivity over social cohesion.
I speak with no authority. I don’t even know how such a theory could be tested.
I don't know about papers but I had a doctor tell me they are overrepresented among snipers in the military. ADD could be an advantage to hunting.
1. How is it advantageous?
2. Assuming it really is: Why would this make it unlikely to be encoded on a single gene? As a layman, the only condition I'm aware of with this "downside but also upside" quality is sickle cell anaemia (downside is anaemia, upside is increased resistance to malaria), which is decided by a single nucleotide change on chromosome 11.
32 y/o male. I took an in-person assessment earlier this year. It was an 8 hour battery of tests split across two days. In no particular order:
- Clinical Interview
- Wechsler Adult Intelligence Scale – Fourth Edition (WAIS-IV)
- Wechsler Memory Scale – Fourth Edition (WMS-IV)
- Conners Continuous Performance Test – Third Edition (CPT-3)
- Delis-Kaplan Executive Functioning System, selected subtests
- Wisconsin Card Sorting Test (WCST)
Are you familiar with any of those? I did some research after receiving my report and apparently the combination of tests listed above are well-respected, about as good as it gets. I’m curious what your take is.
The subjective part of the assessment was actually the clinician making sense of the data. My cognitive assessment (IQ and its subtypes) scored fairly high, I averaged something like 115 (84th percentile). But my memory assessment scores (audio/visual memory/working memory, immediate/delayed memory) tanked tremendously, I averaged around 90 (30th percentile).
My positive diagnosis was based on the variability of scores and the clear cognition-memory gap. The results made sense, aligned with my experience in life (I fell asleep in almost every lecture in college, sustaining attention while taking notes was a heavy audio-visual working memory exercise for me).
I personally haven’t adopted any of this as my identity but it opened a door to do some metacognition and reflect on how I interface with the world. Also the stimulant medication didn’t magically fix everything, sometimes the hyper focus is worse, but there was one HUGE benefit that I didn’t realize I was missing - emotional regulation. I’m a heavy ruminator and pretty much suffered in silence most of my life, my inner dialog is much more organized and calm, and I can comb through my thoughts easier now.
P.S. I cannot recommend enough - check out “HealthyGamerGG” on YouTube. He does some deep dives on ADHD and other diagnoses. Classically trained psychiatrist with something like 5 years of training as a Buddhist monk. Very insightful guy who’s both data-driven and spiritual, helping a lot of people.
Isn't this true of nearly all mental disorders in DSM-5 and ICD-11?
We don't really know what mental disorders are and so we don't have objective diagnostic tests for them. [1]
We just have treatments that sometimes work for some people (and with the replication crisis[2] that sometimes is probably a lower value than expected).
[1] https://pmc.ncbi.nlm.nih.gov/articles/PMC6732705/
[2] https://pmc.ncbi.nlm.nih.gov/articles/PMC5835722/
ADHD is not an autism spectrum disorder, is it?
That’s my bad for conflating the two. Indeed they are not the same in ICT-11 but! diagnostics is moving towards the direction of treating them the same. ADHD and ASD have extremely high comorbidity and it has been proposed many times to classify them together because the symptoms overlap (difficulties at school, aggressive behaviour or temper, lack of social skills, etc). In fact it has become so difficult to find distinctive features of ADHD both in diagnostics AND treatment (both are usually treated with cognitive behavioural therapy and in more severe cases medication) that it has been proposed numerous times to drop their distinction in the ICT, but this hasn’t happened yet. Good paper to the point:
https://pmc.ncbi.nlm.nih.gov/articles/PMC4654237/
Autism Disorder with High Distractability?
I believe AuDHD is the common term.
The gold edition
No, however they are often comorbid.