Monday 30 March 2015

#Germanwings, Missionary Psychiatrists, and Bayes’ Theorem


Every profession contains actuaries and missionaries, the latter more frequent because every profession is a conspiracy against the laity. To drum up business, psychiatrists have tended to suggest that people have many psychological problems which, if left untreated, could have bad consequences. It is part of the psychiatric missionary drive to find damaged souls and heal them, pouring the sanctifying oil of therapy on the wounds of sin. This means sermonising about the many deficiencies of mind to which the public are prone, and the many treatments available to cure them. Many are ill, the sermons claim, and most of them would benefit from treatment, and delay in seeking professional advice would be a mistake, often a dangerous one.

Psychiatrists have a problem: if psychiatric illness is a real condition, then it is one that most people want to avoid, and avoiding those who have the illness is one obvious strategy. No one is sure from whence madness springs, and behavioural contagion from those already mad may be one means of transmission, a notion which the behaviour of many psychiatrists does little to discourage.

The salesmen of psychiatry are left with a curious sales pitch: personal problems and behavioural disorders are in fact psychiatric illnesses; these illness are not contagious; the afflicted are behaviourally disturbed but can be made better; they may be a little more dangerous, but not much; and, above all, any reaction other than sympathy and support is reprehensible. Psychiatric illnesses must not be stigmatised, and even precautionary restrictions are part of stigmatisation, so must not be applied.

The actuaries of psychiatry are in a minority, or perhaps they just get less publicity. They tend to pour cold water over therapeutic claims, and turn up harsh facts about the profound severity and persistence of many severe psychiatric conditions. For example, these actuaries also report that patients with schizophrenia are 5 times as dangerous as patients without it.

Of course, the competing demands of the missionary and the actuarial perspective depend on context and the public presentation of psychiatry, and some practitioners are involved in both activities. In the aftermath of Germanwings the missionary tendency have been counselling against “kneejerk reactions” and “stigmatisation”, a position with which I agree.

Leading the charge on behalf of his profession, Professor Sir Simon Wessely, President of the Royal College of Psychiatrists, said: "We should be careful not to rush judgements. Should it be the case that one pilot had a history of depression, we must bear in mind that so do several million people in this country.

"Depression is usually treatable. The biggest barrier to people getting help is stigma and fear of disclosure. In this country we have seen a recent fall in stigma, an increase in willingness to be open about depression and most important of all, to seek help.

"We caution against hasty decisions that might make it more difficult for people with depression to receive appropriate treatment. This will not help sufferers, families or the public."

I truly hesitate to question the arguments attributed to the redoubtable Sir Simon, because the comments may be inaccurate, and are probably drawn from a much longer interview in which many conditional phrases will have been dropped. I agree with many of the points Simon makes. However, in playing the ball, not the man, suppose anyone had advanced the argument:“Should it be the case that one pilot had a history of depression, we must bear in mind that so do several million people in this country.” That particular argument misses the point: we are not talking here about millions in the country; we are talking about the state of mind of pilots, a highly select minority occupation, entrusted with other people’s lives.

In the OJ Simpson trial the defence argued that it would be wrong to put before the jury the fact that OJ Simpson had previously assaulted his wife, arguing that only 0.1% of wife-beaters went on to murder their wives. The judge and the prosecutors, despite getting advice, accepted that argument. Of course, OJ Simpson was not on trial for wife-beating but for murder, so the real question was: if a married woman is murdered, what is the probability that the murder was committed by a man who had previously beaten her? The answer: 81%. The jury should have been told that, but they were not.

Most depressed people do not go on to do anything bad. Among those pilots who have put the plane into a dive are many with psychological problems. We are working to avoid one specific category of risk: being killed by the deliberate action of a pilot. What matters is to understand those cases, few as they have been, and to see if they can be avoided. Crucially, can cases like these be avoided by excluding people with a history of severe psychiatric illness from being commercial airline pilots?

Here is a list of probable cases, but I do not know if it is exhaustive:

I believe that such exclusions would be prudent. They would come at a cost, namely that some fine pilots with depression would be barred from their chosen occupation, but all precautions come at a cost. It would be prudent even if unfair, though better detection rates might, just possibly, reduce the number of pilots falsely excluded. The reason for exclusion is that the safety of the passenger trumps the occupational ambitions of the pilot. There are plenty of candidates: why not follow the usual airline industry practice of reducing risk to the absolute minimum?

Air safety has improved precisely by reducing every single category of risk, even if the actual rate of that particular problem is low. Every accident, however freakish, is investigated so that the error can be purged out of the system. I was once on a flight which was turned round on a clear day because the second (backup) artificial horizon indicator had malfunctioned. Both airports in Europe were in bright sunshine, and the horizon was clearly visible, but rules were rules. On landing for the 15 minute repair the crew were told that if they continued the flight they would have exceeded their permitted flying time, so we waited two hours for new crew. Safety first.

Naturally, policy on pilot screening must be well-considered and based on evidence, but if it turns out the co-pilot had depression requiring 18 months of treatment then this must be flagged up as a risk factor immediately. The torrent of revelations, leaks, and unaccountable briefings by unnamed persons is the modern way of investigating events in a highly connected digital society, and it is fruitless to wish it otherwise. However, policy is a different matter. However, it does not have to take very long. Some policies are applied very quickly. After  Air France 447 went down in the Atlantic air speed indicators were changed very quickly to ones that were less likely to ice up.

Although facts or allegations about the co-pilot have come out in a torrents, and we need hard facts before coming to a judgment about him as an individual, we have sufficient circumstantial pointers to begin a general debate about the psychological assessment and monitoring of pilots. On that point, my psychiatric colleagues may feel I am laying into them unfairly, but there is no evidence that psychologists are any better than them in the detection game, not only the detection of disorder but most importantly in the detection of liars. Pilots are highly motivated to lie: they undergo a long training in order to get a prestigious and usually well-paid job. They will be very tempted to downplay psychological problems.

So, how good are the psycho-clinicians at predicting human behaviour?Psychiatric actuaries have been keeping quiet. Depression often reoccurs, and the best predictor of depression in any period is previous episodes of depression. Statistical prediction is usually better than clinical prediction, as Meehl argued in 1954. That supposedly cunning, penetrating, highly sophisticated face to face interview is less predictive than actuarial data obtainable by diligent recording of major behavioural events.

Meehl, P. E. (1954). Clinical versus statistical prediction. Minneapolis: University of Minnesota Press

Seven factors appear to account for the failure of mental health professionals to apply in practice the strong and clearly supported empirical generalizations demonstrating the superiority of actuarial over clinical prediction.

The list below is taken from Meehl’s “Causes and Effects of My Disturbing Little Book” Journal of Personality Assessment, 1986, 50(3), 370-375.

1. Sheer ignorance: It amazes me how many psychologists, sociologists, and social workers do not know the data, do not know the mathematics and statistics that are relevant, do not know the philosophy of science, and are not even aware that a controversy exists in the scholarly literature. But what can you expect, when I find that the majority of clinical psychology trainees getting a PhD at the University of Minnesota do not know what Bayes’ Theorem is, or why it bears upon clinical decision making, and never heard of the Spearman–Brown Prophecy Formula!

2. The threat of technological unemployment: If PhD psychologists spend half their time giving Rorschachs and talking about them in team meetings, they do not like to think that a person with an MA in biometry could do a better job at many of the predictive tasks.

3. Self-concept: “This is what I do; this is the kind of professional I am.” Denting this self-image is something that would trouble any of us, quite apart from the pocketbook nerve.

4. Theoretical identifications: “I’m a Freudian, although I have to admit Freudian theory doesn’t enable me to predict anything of practical importance about the patients.” Although not self-contradictory, such a cognitive position would make most of us uncomfortable.

5. Dehumanizing flavor: Somehow, using an equation to forecast a person’s actions is treating the individual like a white rat or an inanimate object, as an it rather than as a thou; hence, it is spiritually disreputable.

6. Mistaken conceptions of ethics: I agree with Aquinas that caritas is not an affair of the feelings but a matter of the rationally informed will. If I try to forecast something important about a college student, or a criminal, or a depressed patient by inefficient rather than efficient means, meanwhile charging this person or the taxpayer 10 times as much money as I would need to achieve greater predictive accuracy, that is not a sound ethical practice. That it feels better, warmer, and cuddlier to me as predictor is a shabby excuse indeed.

7. Computer phobia: There is a kind of general resentment, found in some social scientists but especially people in the humanities, about the very idea that a computer can do things better than the human mind. I can detect this in myself as regards psychoanalytic inference and theory construction, but I view it as an irrational thought, which I should attempt to conquer.

After 29 years it is a somewhat dated list, but not that dated. To my amazement the current US pilot evaluations still include the Rorschach test.

A quick summary of current findings in pilot selection: Emotional stability and Conscientiousness are the prized personality characteristics of pilots. Generally speaking pilot applicants are more extraverted and tough minded than the general population. Applicants who fail in training are more introverted and depressed than successful candidates. Dropouts are more anxious, and also more conscientious (perhaps this picks up obsessionals). Subsequently, higher performance is associated with lower levels of anxiety and depression, usually picked up in personality questionnaires as high Neuroticism. All those are what one might call the “Select In” variables that are searched for in applicants. Of equal interest are the “Select Out” variables which lead to being dropped from piloting: psychosis, major depression and anxiety disorders. (If it is really true that the young Germanwings co-pilot had experienced major depression he should have been dropped).

The dilemma faced by psychiatry is that it must champion humane treatment, guard against public anxiety about the mentally ill, while also being absolutely fair minded about actual risks. All clinicians must respect the patient, and also respect the facts. Flying is safe because some many errors have been squeezed out of the system. We are now at the point when many of the remaining errors are human ones. My view is that major psychiatric illness should be a bar to being a commercial airline pilot.

I am sorry this post is too long. I did not have time to make it shorter.


  1. The Lion makes a case that the problem was schizophrenia and not depression.

    Lubitz received Olanzapine injection in 2010 | Lion of the Blogosphere

    Along with his many other recent post on the matter.

    It's worth pointing out that Greg Cochran and Paul Ewald once made the case that pathogens are heavily involved in common mental illnesses (even though they are highly heritable). So indeed they could be "catching", ironically.

    I'm sure there's a cost-benefit analysis that can be done to weight the merits of screening. Intense screening might however create a perverse incentive for pilots to hide whatever symptoms of mental illness they might suffer (see the episode of House: "The Right Stuff").

  2. "Greg Cochran and Paul Ewald once made the case that pathogens are heavily involved in common mental illnesses": it's my guess that pathogens are heavily involved in all sorts of things - e.g. that they might explain the mysterious rise and fall of heart attacks. After you get past broken legs and the like, it's all genes and germs.

  3. It’s wonderful to read a post that begins with Thorstein Veblen & ends with Paul Meehl!

    “…major psychiatric illness should be a bar to being a commercial airline pilot.”

    You hit the nail on the head. Or the mountain with the cockpit, as Lubitz would say.

    Projectives like the Rorschach are practically useless - & are totally useless for screening motivated, bright potential pilot types – the few who have any bizarre ideations are not going to let them slip out.

    In the US when the FAA sends pilots/potential pilots to seek specialized testing by clinical or neuropsychs (e.g., commercial pilots seeking reinstatement after treatment for ETOH abuse or depression, or initial license seekers who were diagnosed with AD/HD when younger) - the FAA demands overkill testing with individually administered outmoded standard batteries, subjecting the person to at least 2 full days of testing of (often) poorly normed tests not predictive of any clear criterion/criteria (batteries/tests such as Halstead Reitan, Trails Making, draw a clock, Wechsler, etc.) These testing requirements became codified to give the appearance of scientific respectability, but they don’t predict jack - it’s all muddy tea leaves - or a racket to allow psychologists who don’t understand measurement to earn money!

  4. I was also surprised by the Trail Making test, though it might have some links with route finding, though in that case it would be better to test route finding. I think they need to go in another direction, and look at detection of lies. Difficult, but not totally impossible.

  5. In vino veritas, Dr T.

  6. Mr. Thompson,

    In today's outcome-obsessed society, people must become countable, quantifiable, transparent. And this leads to a GROTESQUE new misunderstanding of psychotherapy. Therapy is now conceived as a set of techniques that can be applied to a human being. This makes sense if we see it as a business transaction with a buyer, a seller and a product. But it totally ignores the most basic fact: that therapy is not like a plaster that can be applied to a wound, but is a property of a human relationship. Therapy is about the encounter of two people, and the real work is done not by the therapist but by the patient. As the psychoanalyst Donald Winnicott observed, the therapist provides a space in which the patient can construct and create something. The therapist encourages and facilitates, but whether a therapy takes place or not depends entirely on the patient.

    The patient's own reality has to be taken very seriously by the psychiatrist. To explore it, to define it, to elaborate it and to see where it will go. No outcome can be predicted in advance. With most psychiatry today the divided self has vanished, along with the recognition that grief, despair and frustration strike at the heart of our image of self-possession and fulfilment.