7 ms·

Ontology of Psychiatric Conditions: Taxometrics

104 points by bschne 6y ago

iainmerrick 6y ago
This is a great read; it very clearly crystallizes and expresses a concept I think I had mostly figured out but not in any coherent way. It reminds me of a pet peeve of mine, the term “on the spectrum” for autistic people. The key part of a spectrum is that everybody is on it, that’s what makes it a spectrum! By implicitly allowing some people to be “off the spectrum”, you’re having your cake and eating it.
- pas 6y ago
  Might be relevant: https://psyche.co/ideas/lets-avoid-talk-of-chemical-imbalance-its-people-in-distress https://psyche.co/ideas/lets-avoid-talk-of-chemical-imbalanc...
- SamoyedFurFluff 6y ago
  I was under the impression “on the spectrum” actually referred to the spectrum(or collection) of extreme behaviors that collectively form to indicate autism, not that there is a singular “more/less” well defined autistic behavior that simultaneously exists in all people.
- smeej 6y ago
  That would be "on a spectrum," not "on the spectrum." Wavelengths are all on a spectrum. Any particular wavelength may or may not be on the visible light spectrum, for example. "The autism spectrum" does not and has never meant a whole spectrum of all people, some of whom are just "autistic enough" to be considered "on the spectrum." The vast majority of people simply aren't on the autism spectrum at all.
  - lcuff 6y ago
    I mostly agree with you, but as somebody who is not on the autism spectrum 99% of the time, I still have had moments where I'm incredibly socially awkward, as most folks have had. Add this kind of temporal factor, and the spectrum spreads to cover us all, though there are still useful questions to ask: Is this person awkward enough so much of the time that he/she wouldn't make a good <x>. (Teacher/therapist/salesman/politician). The complexity re-emerges, we all have a spectrum of personality characteristics that includes autistic characteristics.
    - smeej 6y ago
      Having some traits that resemble autism isn't the same as having an atypical brain. Autism doesn't just mean, "Damn this person is really awkward." If you look into the screening tools, you'll realize many of the questions are actually about sensory processing, not just human interaction. If there were a spectrum of human awkwardness, sure, everybody could be on it somewhere, but that's not what the autism spectrum is.
      - iainmerrick 6y ago
        Having some traits that resemble autism isn't the same as having an atypical brain. But even assuming that's true (which I don't think is actually known) how would you distinguish them? There isn't yet a genetic test or an antibody test or anything like that to distinguish autistic from non-autistic people, right? So it's based on judging the symptoms; and given there's a wide spectrum of symptoms, the categorisation is always going to be somewhat arbitrary.
        zepto 6y ago
        I think that the results of the study in question suggest that you can distinguish a real systematic difference even from the stochastic data.
        skissane 6y ago
        In practice, reliably distinguishing ASD from non-ASD is problematic. [0] is a PhD thesis which (in its first part) examines three specialist ASD diagnostic clinics in the US, with a >30% percentage point difference in diagnosis rates. It argues that the best explanation for that observed difference is differences in clinical culture between the clinics; and, that despite this substantial variation in diagnosis rates, the clinics took an unusually rigorous approach to diagnosis, suggesting that in a broader set of clinics (most of whom would approach diagnosis with less rigour) the variation is likely to be even higher. Although we have diagnostic instruments, such as the ADOS-2 (which along with the ADI-R is considered the "gold standard"), they have problems. One problem is that the standards for using these instruments clinically are a lot weaker than the standards for research use. [1] is a study which attempts to measure the accuracy of ADOS(-2) coding by clinicians, by comparing it to the consensus coding of experienced researchers – it found a high variability in the accuracy of the clinical codings – some clinicians were quite close to the research standard, others were a fair way off. [0] https://dspace.mit.edu/handle/1721.1/90070 https://dspace.mit.edu/handle/1721.1/90070 [1] https://pubmed.ncbi.nlm.nih.gov/29560529/ https://pubmed.ncbi.nlm.nih.gov/29560529/
  - skissane 6y ago
    > The vast majority of people simply aren't on the autism spectrum at all. What about the broad autism phenotype (BAP)? BAP is very common in close relatives of people diagnosed with ASD. And there is no clearcut boundary between ASD and BAP – the boundary varies from clinician to clinician. (On that topic, see [0] which argues that a >30 percentage point difference in ASD diagnosis rates between two specialist clinics is best explained by differences in the culture of the clinicians.) If ASD is 1-2% of the population, BAP could be several times that. [0] https://dspace.mit.edu/handle/1721.1/90070 https://dspace.mit.edu/handle/1721.1/90070
  - iainmerrick 6y ago
    The vast majority of people simply aren't on the autism spectrum at all. Well, that's the bit I'm questioning, although I'm definitely no expert. This Astral Codex Ten post would seem to back me up, although on re-reading it's more ambiguous: Autism is such an annoying thing to have on this list – just when everyone finally agreed there was an “autism spectrum” and no clear difference between neurotypical-people-with-some-autistic-traits and high-functioning-autistics, along comes this meta-analysis to say nope, it’s a taxon, neurotypicals and autistics are two clear objectively separate categories. I did hunt down the studies here and they actually seemed pretty good. But none of these results are strong enough to be more than suggestive, so I am going to keep believing in an autism spectrum until more research comes in. I don't know enough to rate the research here. But it does seem to me a bit strange to work so hard on communicating to laypeople that there isn't just a single condition called "autism", it's a whole spectrum with degrees of severity, but at the same time to still insist that only a small discrete set of people "have autism" and the rest of us are completely free and easy. As other commenters have noted, all the symptoms of low-level autism (social awkwardness, sensitivity to overstimulus, difficulty in communication, etc) are things that almost everybody experiences now and then. So it seems much more helpful to me to think of autistic symptoms as things that everybody has to a greater or lesser degree; so the autistic spectrum has room for everybody.
    - zepto 6y ago
      Another possibility is that these kinds ‘symptoms’ are second order effects which everyone exhibits to some degree, but that autism itself is not. For example - here are some possible causes of a person exhibiting social awkwardness: 1. Slow/Deep processing of language 2. Distraction by other stimuli such as bright lights, visual noise. 3. Introversion 4. Lack of experience in the particular social setting. 5. Religious structures agains certain prevailing social behaviors. 6. A headache caused by forgetting to hydrate adequately during exercise. 7. A pressing need to empty one’s bladder. 1 & 2 are often associated with Autism, but 4 could result from 1 & 2 making social situations unrewarding. 6 & 7 could just be rare flukes or they could happen frequently due to ADHD. The point I’m getting at is that Autism (or ADHD) can be conditions with varying degrees of severity and that can be orthogonal to the fact that the symptoms present in a spectrum across the entire population, because each ‘symptom’ has many causes and is fundamentally stochastic.
- skissane 6y ago
  > It reminds me of a pet peeve of mine, the term “on the spectrum” for autistic people. That's a pet peeve of mine too, but for a different reason – there is more than one spectrum in the DSM-5. There is a whole big section entitled "Schizophrenia Spectrum Disorders and Other Psychotic Disorders". The concept of "obsessive compulsive spectrum" was also considered for inclusion in DSM-5, but ultimately didn't make it, but if you look at the work group list inside the front matter, one of the work groups was called "Anxiety, Obsessive-Compulsive Spectrum, Posttraumatic, and Dissociative Disorders". And there are other spectrums discussed in the literature of psychology and psychiatry, such as the "bipolar spectrum", although that isn't mentioned in the DSM-5. People who say "the spectrum" instead of "the autism spectrum" appear to be ignorant of those other spectrums.
tgbugs 6y ago
The author is nearly there, but they are lacking a few key pieces in their ontology and thus their language traps them by forcing them to conflate concepts that in fact need to be decoupled. The required concepts are as follows 1. condition or underlying biological etiology 2. diagnostic codes 3. symptoms 4. the patient 5. the person assigning the code to a patient 6. the impact of the symptoms on patient quality of life (this one is nearly always left out, I left it out before I noted as I was wrapping up the post) There are a number of relationships between these that I won't go into in detail, but to give one example, there is "some underlying condition may give rise to some symptoms." The problem the author complains about is an inevitable artifact cause by discretization of underlying continuous variables into discrete categories. This is a direct consequence of signal detection theory and is why you see things described as spectrum disorders, because diagnostic codes are applied to sets of symptoms that are produced by multiple different underlying etiologies, including underlying conditions which would fall into the category of "normal" in the population. This is exacerbated by the fact that there is significant variability in how the person assigning the codes assesses the symptoms. An example example of this is that medical professionals consistently underestimate the amount of pain experienced by black Americans [1], and this is pain which is about is unambiguous as you can get. The question then becomes, can we measure the various biases in these systems to try to recover what is really going on. Usually the answer is no. In the case of Alzheimer's disease post mortem pathology is absolutely required in order for a diagnosis to be confirmed, and we don't do enough autopsies to improve our models for mapping behavioral diagnosis to the pathology (which is definitional). This situation may improve over time, but as long as we cannot directly measure underlying etiology, those who may or may not suffer from an underlying condition will continue to be subjected to the current, clearly inadequate, system. 1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4843483/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4843483/
- pmayrgundter 6y ago
  Right on. Without etiology you have no mechanism and thus no hypothesis. This leaves unsolved the ambiguity between correlation and causation. But also agree (I think?) that it is pretty good otherwise. I didn't know that taxometrics existed as a field :-o
- 6y ago
techbio 6y ago
Interesting topic with some clear examples, but then some that completely throw off the track of the article, without clear connections to the examples the article begins with or starts going toward. > So we can just graph GAD-7 scores and then we… >…in fact, this doesn’t work. Let’s look at the flu graph above again. Seems unfinished, in need of reviewing or an editor, and makes steps towards an explanation that remains incomplete.
- Sniffnoy 6y ago
  That part isn't unfinished; it's a rhetorical device. The first ellipsis there represents the speaker realizes that the approach he's about to propose can't be made to work. If you like, imagine it said > So we can just graph GAD-7 scores and then we, uh... >...in fact, this approach doesn’t work. Let’s look at the flu graph above again.
  - techbio 6y ago
    Recognizing the rhetorical device, I still would have liked to see more linkages between the early part of the article and the later sections that address the title topic, especially in the form of charts intelligible to a layperson.
Blikkentrekker 6y ago
> If we wanted to be clever, we could create a multivariate distance measure that combines weight, height, lifespan, IQ, and lots of other ways humans and rabbits could differ, into a 0 – 1 variable where 0 is “most rabbity” and 1 is “most humanish”. Probably these scores wouldn’t overlap at all – if they did, it would mean there’s some human who’s more like a rabbit than some rabbit is, which would be pretty surprising. But even if this were true, it wouldn’t change the fundamental finding that humans and rabbits are pretty different. Or to put it some other way, there’s a fundamental hidden generator producing differences between humans and rabbits (in this case, the species difference). The problem with this model is that it doesn't permit itself to look backwards in time too long. If we were to also consider the organisms that have existed down to the common ancestor of rabbits and humans, it would prove quite a bit more difficult.
potatoman22 6y ago
TL;DR mental illness is a spectrum
- zby 6y ago
  Not really - the point of the article is that we don't know which conditions are on spectrum and which are discrete and it looks that the data we have is just bad.
heikkilevanto 6y ago
I am not much into psychiatry, and not much more into statistics, but I found the article very entertaining to read.

104 points by bschne 6y ago

This is a great read; it very clearly crystallizes and expresses a concept I think I had mostly figured out but not in any coherent way. It reminds me of a pet peeve of mine, the term “on the spectrum” for autistic people. The key part of a spectrum is that everybody is on it, that’s what makes it a spectrum! By implicitly allowing some people to be “off the spectrum”, you’re having your cake and eating it.

pas 6y ago
Might be relevant: https://psyche.co/ideas/lets-avoid-talk-of-chemical-imbalance-its-people-in-distress https://psyche.co/ideas/lets-avoid-talk-of-chemical-imbalanc...
SamoyedFurFluff 6y ago
I was under the impression “on the spectrum” actually referred to the spectrum(or collection) of extreme behaviors that collectively form to indicate autism, not that there is a singular “more/less” well defined autistic behavior that simultaneously exists in all people.
smeej 6y ago
That would be "on a spectrum," not "on the spectrum." Wavelengths are all on a spectrum. Any particular wavelength may or may not be on the visible light spectrum, for example. "The autism spectrum" does not and has never meant a whole spectrum of all people, some of whom are just "autistic enough" to be considered "on the spectrum." The vast majority of people simply aren't on the autism spectrum at all.
- lcuff 6y ago
  I mostly agree with you, but as somebody who is not on the autism spectrum 99% of the time, I still have had moments where I'm incredibly socially awkward, as most folks have had. Add this kind of temporal factor, and the spectrum spreads to cover us all, though there are still useful questions to ask: Is this person awkward enough so much of the time that he/she wouldn't make a good <x>. (Teacher/therapist/salesman/politician). The complexity re-emerges, we all have a spectrum of personality characteristics that includes autistic characteristics.
  - smeej 6y ago
    Having some traits that resemble autism isn't the same as having an atypical brain. Autism doesn't just mean, "Damn this person is really awkward." If you look into the screening tools, you'll realize many of the questions are actually about sensory processing, not just human interaction. If there were a spectrum of human awkwardness, sure, everybody could be on it somewhere, but that's not what the autism spectrum is.
    - iainmerrick 6y ago
      Having some traits that resemble autism isn't the same as having an atypical brain. But even assuming that's true (which I don't think is actually known) how would you distinguish them? There isn't yet a genetic test or an antibody test or anything like that to distinguish autistic from non-autistic people, right? So it's based on judging the symptoms; and given there's a wide spectrum of symptoms, the categorisation is always going to be somewhat arbitrary.
      - zepto 6y ago
        I think that the results of the study in question suggest that you can distinguish a real systematic difference even from the stochastic data.
        skissane 6y ago
        In practice, reliably distinguishing ASD from non-ASD is problematic. [0] is a PhD thesis which (in its first part) examines three specialist ASD diagnostic clinics in the US, with a >30% percentage point difference in diagnosis rates. It argues that the best explanation for that observed difference is differences in clinical culture between the clinics; and, that despite this substantial variation in diagnosis rates, the clinics took an unusually rigorous approach to diagnosis, suggesting that in a broader set of clinics (most of whom would approach diagnosis with less rigour) the variation is likely to be even higher. Although we have diagnostic instruments, such as the ADOS-2 (which along with the ADI-R is considered the "gold standard"), they have problems. One problem is that the standards for using these instruments clinically are a lot weaker than the standards for research use. [1] is a study which attempts to measure the accuracy of ADOS(-2) coding by clinicians, by comparing it to the consensus coding of experienced researchers – it found a high variability in the accuracy of the clinical codings – some clinicians were quite close to the research standard, others were a fair way off. [0] https://dspace.mit.edu/handle/1721.1/90070 https://dspace.mit.edu/handle/1721.1/90070 [1] https://pubmed.ncbi.nlm.nih.gov/29560529/ https://pubmed.ncbi.nlm.nih.gov/29560529/
- skissane 6y ago
  > The vast majority of people simply aren't on the autism spectrum at all. What about the broad autism phenotype (BAP)? BAP is very common in close relatives of people diagnosed with ASD. And there is no clearcut boundary between ASD and BAP – the boundary varies from clinician to clinician. (On that topic, see [0] which argues that a >30 percentage point difference in ASD diagnosis rates between two specialist clinics is best explained by differences in the culture of the clinicians.) If ASD is 1-2% of the population, BAP could be several times that. [0] https://dspace.mit.edu/handle/1721.1/90070 https://dspace.mit.edu/handle/1721.1/90070
- iainmerrick 6y ago
  The vast majority of people simply aren't on the autism spectrum at all. Well, that's the bit I'm questioning, although I'm definitely no expert. This Astral Codex Ten post would seem to back me up, although on re-reading it's more ambiguous: Autism is such an annoying thing to have on this list – just when everyone finally agreed there was an “autism spectrum” and no clear difference between neurotypical-people-with-some-autistic-traits and high-functioning-autistics, along comes this meta-analysis to say nope, it’s a taxon, neurotypicals and autistics are two clear objectively separate categories. I did hunt down the studies here and they actually seemed pretty good. But none of these results are strong enough to be more than suggestive, so I am going to keep believing in an autism spectrum until more research comes in. I don't know enough to rate the research here. But it does seem to me a bit strange to work so hard on communicating to laypeople that there isn't just a single condition called "autism", it's a whole spectrum with degrees of severity, but at the same time to still insist that only a small discrete set of people "have autism" and the rest of us are completely free and easy. As other commenters have noted, all the symptoms of low-level autism (social awkwardness, sensitivity to overstimulus, difficulty in communication, etc) are things that almost everybody experiences now and then. So it seems much more helpful to me to think of autistic symptoms as things that everybody has to a greater or lesser degree; so the autistic spectrum has room for everybody.
  - zepto 6y ago
    Another possibility is that these kinds ‘symptoms’ are second order effects which everyone exhibits to some degree, but that autism itself is not. For example - here are some possible causes of a person exhibiting social awkwardness: 1. Slow/Deep processing of language 2. Distraction by other stimuli such as bright lights, visual noise. 3. Introversion 4. Lack of experience in the particular social setting. 5. Religious structures agains certain prevailing social behaviors. 6. A headache caused by forgetting to hydrate adequately during exercise. 7. A pressing need to empty one’s bladder. 1 & 2 are often associated with Autism, but 4 could result from 1 & 2 making social situations unrewarding. 6 & 7 could just be rare flukes or they could happen frequently due to ADHD. The point I’m getting at is that Autism (or ADHD) can be conditions with varying degrees of severity and that can be orthogonal to the fact that the symptoms present in a spectrum across the entire population, because each ‘symptom’ has many causes and is fundamentally stochastic.
skissane 6y ago
> It reminds me of a pet peeve of mine, the term “on the spectrum” for autistic people. That's a pet peeve of mine too, but for a different reason – there is more than one spectrum in the DSM-5. There is a whole big section entitled "Schizophrenia Spectrum Disorders and Other Psychotic Disorders". The concept of "obsessive compulsive spectrum" was also considered for inclusion in DSM-5, but ultimately didn't make it, but if you look at the work group list inside the front matter, one of the work groups was called "Anxiety, Obsessive-Compulsive Spectrum, Posttraumatic, and Dissociative Disorders". And there are other spectrums discussed in the literature of psychology and psychiatry, such as the "bipolar spectrum", although that isn't mentioned in the DSM-5. People who say "the spectrum" instead of "the autism spectrum" appear to be ignorant of those other spectrums.

tgbugs 6y ago

The author is nearly there, but they are lacking a few key pieces in their ontology and thus their language traps them by forcing them to conflate concepts that in fact need to be decoupled. The required concepts are as follows 1. condition or underlying biological etiology 2. diagnostic codes 3. symptoms 4. the patient 5. the person assigning the code to a patient 6. the impact of the symptoms on patient quality of life (this one is nearly always left out, I left it out before I noted as I was wrapping up the post) There are a number of relationships between these that I won't go into in detail, but to give one example, there is "some underlying condition may give rise to some symptoms." The problem the author complains about is an inevitable artifact cause by discretization of underlying continuous variables into discrete categories. This is a direct consequence of signal detection theory and is why you see things described as spectrum disorders, because diagnostic codes are applied to sets of symptoms that are produced by multiple different underlying etiologies, including underlying conditions which would fall into the category of "normal" in the population. This is exacerbated by the fact that there is significant variability in how the person assigning the codes assesses the symptoms. An example example of this is that medical professionals consistently underestimate the amount of pain experienced by black Americans [1], and this is pain which is about is unambiguous as you can get. The question then becomes, can we measure the various biases in these systems to try to recover what is really going on. Usually the answer is no. In the case of Alzheimer's disease post mortem pathology is absolutely required in order for a diagnosis to be confirmed, and we don't do enough autopsies to improve our models for mapping behavioral diagnosis to the pathology (which is definitional). This situation may improve over time, but as long as we cannot directly measure underlying etiology, those who may or may not suffer from an underlying condition will continue to be subjected to the current, clearly inadequate, system. 1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4843483/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4843483/

pmayrgundter 6y ago
Right on. Without etiology you have no mechanism and thus no hypothesis. This leaves unsolved the ambiguity between correlation and causation. But also agree (I think?) that it is pretty good otherwise. I didn't know that taxometrics existed as a field :-o
6y ago

techbio 6y ago

Interesting topic with some clear examples, but then some that completely throw off the track of the article, without clear connections to the examples the article begins with or starts going toward. > So we can just graph GAD-7 scores and then we… >…in fact, this doesn’t work. Let’s look at the flu graph above again. Seems unfinished, in need of reviewing or an editor, and makes steps towards an explanation that remains incomplete.

Sniffnoy 6y ago
That part isn't unfinished; it's a rhetorical device. The first ellipsis there represents the speaker realizes that the approach he's about to propose can't be made to work. If you like, imagine it said > So we can just graph GAD-7 scores and then we, uh... >...in fact, this approach doesn’t work. Let’s look at the flu graph above again.
- techbio 6y ago
  Recognizing the rhetorical device, I still would have liked to see more linkages between the early part of the article and the later sections that address the title topic, especially in the form of charts intelligible to a layperson.

Blikkentrekker 6y ago

> If we wanted to be clever, we could create a multivariate distance measure that combines weight, height, lifespan, IQ, and lots of other ways humans and rabbits could differ, into a 0 – 1 variable where 0 is “most rabbity” and 1 is “most humanish”. Probably these scores wouldn’t overlap at all – if they did, it would mean there’s some human who’s more like a rabbit than some rabbit is, which would be pretty surprising. But even if this were true, it wouldn’t change the fundamental finding that humans and rabbits are pretty different. Or to put it some other way, there’s a fundamental hidden generator producing differences between humans and rabbits (in this case, the species difference). The problem with this model is that it doesn't permit itself to look backwards in time too long. If we were to also consider the organisms that have existed down to the common ancestor of rabbits and humans, it would prove quite a bit more difficult.

potatoman22 6y ago

TL;DR mental illness is a spectrum

zby 6y ago
Not really - the point of the article is that we don't know which conditions are on spectrum and which are discrete and it looks that the data we have is just bad.

heikkilevanto 6y ago

I am not much into psychiatry, and not much more into statistics, but I found the article very entertaining to read.