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Comment by jaggederest | Hacker News Reader

ADHD in particular is located to very specific areas in the brain. Primarily the dorsolateral prefrontal cortex and areas in the cingulate cortex. We can see neuroanatomy differences on scans, which, while not specific or sensitive enough for diagnosis, are definitely real physical changes in the brain, and they're pretty consistent across diagnosed vs baseline.

There are lots of psychiatric disorders where that doesn't take place, but developmental neuropsychiatric disorders don't fall under that "are they even alike at all" kind of umbrella. In some kind of awful alternate universe we could pretty reliably induce them with gamma knife surgery, for example.

Depression is much easier to argue that it's a less specific symptom of a larger constellation, with lots of causes and lots of manifestations.

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Can you point me to a study showing these brain scans being different from those with diagnosed ADHD and not? The evidence would furthermore have to show that this difference is apparent not just from adhd vs non adhd but adhd vs anxiety, depression etc. And lastly, are these changes perhaps an affect of taking stimulants?

And how significant are these results? Are we talking about a few percent difference? Are 10% of diagnoses ADHD shown to have statistically significant differences, 20, 50, 90? Depending on the figure, my criticism of the diagnostic criteria remains. Because if it is a low figure like 10%, that means 90% of the diagnoses aren't supported by any scientific evidence.

From what I've been told, including professionals this evidence does not exist.

I've also seen studies which indicate that psychiatric evaluations are entirely inconsistent across physicians.

> The morphometric findings predicted an ADHD diagnosis correctly up to 83% of all cases.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5391018/

It's not good enough for diagnosis - you want to hit 95+% accuracy for diagnostic. And MRIs are extremely expensive compared to 2-3 outpatient psychology appointments. But it's real.

I admit the study looks pretty good, but Id still have to see if these changes are present in those with depression/anxiety, etc and 2. are not result of stimulant use to be convinced. I found this if youre interested which cites more studies https://ajp.psychiatryonline.org/doi/full/10.1176/appi.ajp.2...

>It's not good enough for diagnosis - you want to hit 95+% accuracy for diagnostic.

This doesn't quite make sense to me, because you're comparing it to the current diagnostic criteria and assuming it to be 100% accurate.

If we want to be totally scientific, we ought to just do these scans and diagnose people with low gray matter volume, etc and drop the DSM, ADHD etc.

And if we start scanning tons of brains and finding out that X% of people with low gray matter volume do not exhibit any ADHD symptoms?

Bayes strikes again.

> https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5391018/

Two major problems with studies like this:

1. The number of brain sub-regions and associated variables they're looking at is huge. Perhaps more than the number of patients in the study, depending on how you look at the data. If you collect enough data points on two groups of about ~30 people each and you run enough regressions, eventually you'll find some model that works on your small data set. This would need to be tested against a much larger cohort.

2. They did not control for stimulant usage at all. In fact, they note that stimulant use was vastly higher in the ADHD group, because obviously you need an ADHD diagnosis to receive ongoing stimulant prescriptions. It's a delicate topic, but we know that stimulant use in some cases is associated with changes in brain structure and blood flow. It's a huge variable that is hard to control for in a study like this.

Overall, I don't find a study with 31 ADHD patients that tested dozens and dozens of different variables to be all that conclusive. Perhaps useful for focusing future research, but a singular study like this isn't very conclusive.

I think there's also another critical issue that plagues every single observational study - the direction of causality. Our behaviors can and do physically change every single aspect of our body, including our brains. For instance chess masters not only activate different parts of their brain when playing chess than amateurs, but also have observable morphometric differences in their brains. [1]

If the direction of causality there was not overtly obvious (as nobody starts out anything even close to a master), one could easily assume those differences caused one to be a master, rather than vice versa. It's the exact same issue here, except the direction of causality is unclear. You're seeing a shared morphometric difference among people of some trait (ADHD) and then just assuming that that difference causes ADHD, rather than that ADHD causes the difference!

To even assume this is the case one would need to perform MRIs on random very young individuals prior to ADHD diagnoses, and then make a prediction, based solely on that MRI, on which ones would be diagnosed with ADHD with no input or information given to the participants before a follow study in a decade or so. That study would then help prove the direction of causality that's seemingly just simply being assumed in this one.

[1] - https://www.frontiersin.org/journals/neuroscience/articles/1...

In a world where we had precision tools that could be used to deliberately alter brain morphology, the direction of causality would be highly relevant for trying to treat ADHD -- it would tell us whether there is any point in trying to use those tools. But for diagnosis only, I don't think the direction is actually relevant. That is, if we see a strong correlation between ADHD behaviour (as measured by, say, a standardised written test) and certain brain morphologies, then we're justified in concluding that ADHD has some objective physical manifestation -- that is, that the written tests aren't just measuring arbitrary collections of symptoms, they're estimating "something real". There might still be many different underlying causes.

Would this be useful? I think so: It would then be possible to assess the accuracy of a written test.

I think the risk of conflation with stimulant use that another poster mentioned is very real, though, and that problem is a close cousin of the "direction of causality" problem.

This is true and quite an interesting and nuanced point. But the connotation of this discussion, and something I expect applies to the overwhelming majority of people, is an association of physical manifestation (brain morphometrics or whatever) causes issue, rather than issue causes physical manifestation.

In particular this whole thread of discussion started back with somebody expressing a bit of skepticism about the definitive nature of ADHD (and other psychiatric disorders) and somebody responded with the brain morphometrics as proof of such, yet in reality that's mostly still just begging the question.

According to this, stimulant use if anything normalizes the differences found. Without a proper understanding of the field, I have to admit its hard to criticize the specifics. https://ajp.psychiatryonline.org/doi/full/10.1176/appi.ajp.2...

That said, all these studies are done way after ADHD was established. That is, ADHD as a concept wasn't established by looking at neurological brain scans or any kind of physical evidence. Makes me wonder what the exact thought process was for establishing the DSM.

I still feel like if I made up a disorder by coming up with 9 semi-normal behaviors as symptoms, enough people would just by chance meet most of the criteria, and imaging scans would find some difference. Wish I was rich so I could conduct that experiment myself.

Unfortunately, the topic of ADHD and brain imaging has been full of bad research and grifters. At the extreme end, people like Dr. Amen were writing books about how ADHD and neuroimaging were correlated, which turned into attempts to sell SPECT imaging for ADHD purposes through his clinics.

Using brain imaging to push questionable psychiatry premises was very popular for a while, and you need to take a lot of research from that era with a huge grain of salt. Remember that with the right settings, neuroscientists can even produce images showing activity in brain regions of completely dead salmon: https://www.wired.com/2009/09/fmrisalmon/

Quite. Psychiatry loves to talk about brain scans and neuroanatomy, but until it dares to actually use them for diagnosis, I think it should be regarded as window dressing.

And you should always read these studies with a careful eye to whether the ADHD subjects are medicated. Often the studies literally measure the effect of the medication and nothing else. (It's a cruel irony for schizophrenics, who are put on antipsychotics that shrivel the cerebral cortex, only to find their shrivelled cerebral cortex brandished as evidence of their supposed dysfunction.)

Also, note that fMRI does not and cannot indicate structural abnormalities in the brain. It just measures current brain activity, as revealed by the flow of magnetically-charged oxygenated blood through the brain. It tells us these people's brains are currently behaving differently from control subjects' brains. Which, it seems to me, is stating the bleeding obvious.

It's a shame that every time someone (e.g. upthread) mentions how even just MRIs are very expensive, often as an excuse for not using such tools, I think of all the times I've heard that other places like India make them quite cheap. Well, it's just one part of a giant pile of problems.

Thanks for the reminder about schizophrenics. Even though I've known about the effect (and especially the effect with use of lithium, which is thankfully not so commonly used), I've sort of forgotten about it as a factor in my thinking about the recent struggles of someone in my personal life. It's probably not forgotten by those working in the system, and wouldn't surprise me if it contributes to the incentives of the system encouraging people to be shut-ins and never challenge anything.

Yeah, I am very troubled by it. I had a friend staying with me last year who I hadn't realised was schizophrenic (a hopelessly vague diagnosis but he undoubtedly had parted company with reality) and off his meds. It was horribly sad. He killed himself a few months later. My mum is a psychiatrist and insists that third-generation antipsychotics are not a 'chemical cosh', which I find doubtful, seeing as so many schizophrenics seem to consider them a worse prospect than unmedicated schizophrenia or death.

We're now giving these drugs to autistics, I gather, and low-dose olanzapine is even being trialled for kids with Asperger's. Compared with lobotomy I suppose it requires less cleaning up.

Since you mention India, I should add that India and other poor countries manage to treat schizophrenia with better remission rates than the UK and US: https://www.nature.com/articles/508S14a

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