Monday, 10 October 2016

What do you mean "invalid"?

Here is a common statement made in debates about psychiatric diagnosis:

"[psychiatric disorder x] is an invalid construct"

This "validity critique" of psychiatric diagnosis arose after the technical overhaul of DSM-III, when the psychometric properties of such classifications became a powerful way of understanding their flaws. Originally, it came from seminal work by Richard Bentall and Mary Boyle, both of whom queried the construct validity and predictive validity of DSM-defined schizophrenia. This was an original and useful way to raise problems with schizophrenia-talk, and it has happily found its way into the mainstream of psychiatric discourse. Unfortunately these contributions get kind of watered down in the endless repetition of a "invalid construct" claim as quoted above. What gets left behind is the veneer of apparent truth, without any substantive meaning.

To say "valid" or "invalid" is not very helpful in itself. Those are words that have both a specific technical psychological meaning and a broader lay meaning. Validity in psychometrics is a term used to describe the extent to which a test or checklist measures something that is actually there or successfully predicts some other event. To understand what is meant by "valid" (or "invalid") we need to ask valid in relation to what? Thus a given questionnaire could be an invalid predictor of suicide, but still be a valid indicator of severely depressed mood.

Psychometric validity is difficult to nail down in the realm of diagnosis because it is not clear what might count as a validating criterion. Bentall and Boyle point out several facts about the diagnosis of schizophrenia, including the fact that symptoms do not cluster together and that functional outcome is not uniform. Those are good things to know, and they undermined pervasive myths about the schizophrenia diagnosis.

But in the broader, lay sense of the terns, it is all but impossible to meaningfully say whether diagnosis [x] is really "valid" or "invalid". What, after all, do those words really mean in this context? The dictionary definition simply suggests "grounded in fact", or "reasonable or cogent". On this definition, surely it is valid to say "I feel ill" (if your first person subjective experience tells you as much), or "I have schizophrenia" (if the technical language using community agrees as such).  If I have a set of experiences that feel subjectively like illness, cause me to meet DSM-criteria for a disorder and that DSM-diagnosis provides a constructive narrative for helping me to live the sort of life I want for myself, is it still an "invalid" diagnosis? In the technical sense of "invalid", it is arguable. In the broader lay sense of "invalid" it seems the answer is a resounding no!

Another way that psychologists increasingly talk of validation is in terms of recognizing the reality of people's experiences. Thus we validate people's sadness or anger by joining with their perspective and agreeing that anger or sadness was a reasonable thing to feel under the circumstances. Failure to do this is called "invalidating", meaning that it seems to undermine the reasonableness of an emotion. Invalidate someone's emotions and you show them they are wrong to have felt them. Invalidate someone's experience of reality and you hint to them that they are crazy.

Talk of lack-of-validity has been a valuable addition to understanding psychiatric diagnosis. But when it gets isolated from its underpinning arguments, validity talk in this context can be invalidating.


  1. Hi

    That's a very clear and concise explainer of validity from a psychometric pov--offhand, I think it might be the best way to describe it to an audience that isn't familiar with all the ins and outs of the discussion (since DSM-III, as you rightly say).

    But I'm a bit confused as to the purpose of the remainder of your post. In that yes, the psychometric properties and discussions of invalidity might well be misunderstood. But IMO, the missing piece of the puzzle is the fact that mental illness isn't unitary. Nor ought it to be automatically invalidating the experience to be told that's one's distress doesn't represent a mental illness.

    What I think I'm trying to say are two things:

    1. Mental illness isn't unitary, and the validity of mental illness isn't often discussed as a cross-cutting broad term--it's the validity of /A/ specific mental disorder, say schizophrenia.

    2. this connects to the point above, because if one takes away the fuzzy mental disorder category set that's indefinable, or at least problematic to define, the residual is a general "distress" axis, to which mental illness is only one contributor.

    So the validity debate is useful for mental health professionals because it defines an illness as separate from other illnesses, as much as it divides Illness from Normalcy. because one presumes that each illness has some unique features whose identification would have additional value. Surely this needs to be stated? I wonder if you have a different ideological position, that militates against stating this explicitly.

    It's been a while since I put this in words, and I must admit my views on validity have evolved so much since I first entered med school. And I still find that its a slippery concept to grasp in all its dimensions.


  2. Thankyou for this comment. It is always nice when someone has obviously read carefully and tried to understand what I am getting at. Perhaps I have been unclear here in what I intended to say so let me try and flesh it out better. We agree that many specific DSM diagnoses leave a lot to be desired in terms of psychometric validity. So the claim that "[X] diagnosis is invalid" makes sense in that context. What I wanted (but I think failed) to bring out is that there are people who would say "I have a diagnosis of [x]", and who would identify that diagnosis as making sense of their experience in a substantive way. Now, we still cannot avoid the fact that diagnosis [x] may not have validity in the professionally defined psychometric sense of that term. However, in the broader, dictionary sense of "valid", things are less clear cut. Is it invalid (in that latter sense) for a person to say "I have an illness called 'x'" where "x" is a psychiatric construct with poor *psychometric* properties? I feel uncomfortable saying it is. So I am left feeling that, absent a context in which it is clearly psychometric validity under discussion, it could be problemtic to simply say "[x] is an invalid term", as it can imply "[x] is an invalid way for anyone to describe or make sense of their experiences". That is why I try to bring out two senses of the term "invalid". I certainly agree with you that the validity debate is useful (in fact essential) for mental health professionals and I also agree it pertains to specific diagnoses, not an illness/non-illness divide. Thus, I don't *think* you have said anything I feel ideologically precluded from stating explicitly. You can point it out to me if I am wrong about that though - our own ideological positions are kind of hard to spot (how could it be otherwise?!).

    Thanks :-)

  3. At a practical level, my experience in an NHS area colonised by Crit Psy, was that if an SU was smart enough to understand the issues around validity and felt invalidated by an imposed formulation, then chances are she probably just wouldn't meet caseness criteria for intervention. Which meant Equivalence Fallacy FTW. There were more than enough people willing to have a formulation imposed on them, such that the odd pesky one clinging to any part of a diagnosis wouldn't be missed or heard. ;)

    Interesting to hear where the "invalid construct" debate began. Do you know the origins of the psychological formulation?

    I like the word "diagnosis". I'm sorry but I do. I think it rolls off the tongue deliciously and combines the elements of the mystical and the esoteric that seem to be equally present in both psychology and psychiatry.

    It's too bad that a "formulation" sounds like something you'd collect from a pharmacy after being diagnosed with an illness!