Friday, December 07, 2007

How This Psychiatrist Thinks About Psychological Tests

First a big thank you to Gerbil for giving me the idea for this post. In a comment on my post "What Good Are Psychologists?" she mentioned psychiatrists who refer patients for diagnostic psychological testing. It got me thinking---this is a good thing---about why I do (or don't do) what I do.

I have to say I hardly ever request psychological tests. Even before I started working in prison, it just wasn't something I routinely did with my patients. When I was in residency we had lectures from psychologists about the different types of tests and what they're indicated for and a few things about interpretation, and later psychologists I've worked with have told me that I have a better understanding of testing than the average psychiatrist, but I'm not sure what that means.

For the lay readers among us, there are some general categories of psychological tests. There are personality tests that measures different character traits. There are intelligence tests that measure IQ. There are projective tests that are used to get an understanding of the person's interpersonal dynamics and style of thinking. There are neuropsychological tests that measure a person's cognitive capacity---ability to learn and remember, use language, coordinate eye-hand movements and so forth.

In general, when thinking about tests you have to consider what it is you're trying to figure out. If you have a patient who is failing in school you might want to order IQ or other achievement tests to see if the personal has a developmental disability or learning disability. If the patient has had a head injury or you think he or she might be getting demented you'd order neuropsychological testing. If you have a patient in therapy and you want material that might be useful to help the patient understand his own inner workings, you'd request projective testing and/or personality testing. Some tests are used as tools to predict certain things: whether or not someone would perform well on a certain job or whether or not they will re-offend as criminals.

It's important for tests to be used as part of an overall patient assessment. Test results fit into a whole database of information that a psychiatrist considers when making a diagnosis or putting together a treatment plan, in addition to a good patient history and a review of available treatment records.

It's also important to know whether or not the given test has been validated for your particular patient because 'normal' test results can be different for different groups of people. A test is only as good as the patients it's been based upon. For example, normal results for the original Minnesota Multiphasic Personality Inventory (MMPI, a test used to diagnose psychiatric disorders) was originally based upon only 500 people living in Minnesota. Much as I would like to think that Minnesota should be the gold standard for normalcy, this just isn't realistic. I mean really---Baltimoreans would end up looking pretty depressed compared to them. This is where a big limitation comes into play for me working in prison---many psychological tests have not been validated for use in prisoners.

Similarly, predictive tests only give group predictions and aren't necessarily reliable for the individual. A certain score on the Hare Psychopathy Checklist might give you a result that the patient has a 15% chance of re-offending, but that just means that out of 100 people with an identical score 85 will not re-offend and 15 will. The score doesn't tell you which of the two groups your patient will actually be in. The other trick with using tests to predict things is that many tests used for prediction have never been proven to have predictive value---there is no test to predict 'good parenthood', for example, yet psychological tests are used constantly in custody evaluations. It's important to know the limits of the test.

So...which tests do I actually use?

In prison the most common test I use is the Mini-Mental State Examination (MMSE). It was invented by two psychiatrists as a quick bedside test of cognitive functioning. You can give it in about ten minutes and it's a great way of measuring how brain impairment changes over time. You use it to check to see if someone's delirium is resolving, or as a screening tool for problems that should be investigated further.

In free society the most common tests I used, besides the MMSE, were general symptom inventories. For example, the Beck Depression Inventory (BDI) is a nice tool for measuring the severity of depressive symptoms. It's used to screen people for depression and also to monitor reponse to treatment.

I never use projective testing, mainly because I've never found it particularly useful for anything---maybe I would if I had a psychotherapy practice but even then I don't know too many psychiatrists who use them. I'd probably use neuropsychological tests if I could, but these are very specialized tests that have to be administered by a neuropsychologist (a subspecialty of psychology) and I don't know of any prisons who have one of those.

So that's my take on psychological tests. Thanks, Gerbil.