The biological approach to treating unhappiness is booming. But is it all it's cracked up to be? Two noted researchers demonstrate that the "scientific" studies that underpin claims of drug effectiveness are seriously flawed—undone by signals from our own bodies. Perhaps the studies really prove the power of placebo—and the absurdity of drawing any line between what is biological and what is psychological.
The air is filled with declarations and advertisements of the power of biological psychiatry to relieve people of their psychological distress. Some biological psychiatrists are so convinced of the superiority of their position that they are recommending young psychiatrists no longer be taught the essentials of doing psychotherapy. Feature stories in such magazines as Newsweek and Time have portrayed drugs like Prozac as possessing almost a mystical potency. The best-selling book Listening to Prozac by psychiatrist Peter Kramer, M.D., projects the idyllic possibility that psychotropic drugs may eventually be capable of correcting a spectrum of personality quirks and lacks.
As longtime faculty members of a number of psychiatry departments, we have personally witnessed the gradual but steadily accelerated dedication to the idea that "mental illness" can be mastered with biologically based substances. Yet a careful sifting of the pertinent literature indicates that modesty and skepticism would be more appropriate responses to the research accumulated thus far. In 1989, we first raised radical questions about such biological claims in a book, The Limits of Biological Treatments for Psychological Distress: Comparisons with Psychotherapy and Placebo (Lawrence Erlbaum). Our approach has been to filter the studies that presumably anchor them through a series of logical and quantitative (meta-analytic) appraisals.
Antidepressants, one of the major weapons in the biological therapeutic arsenal, illustrate well the largely unacknowledged uncertainty that exists in the biological approach to psychopathology. We suggest that, at present, no one actually knows how effective antidepressants are. Confident declarations about their potency go well beyond the existing evidence.
To get an understanding of the scientific status of antidepressants, we analyzed how much more effective the antidepressants are than inert pills called "placebos." That is, if antidepressants are given to one depressed group and a placebo to another group, how much greater is the recovery of those taking the active drug as compared to those taking the inactive placebo? Generous claims that antidepressants usually produce improvement in about 60 to 70 percent of patients are not infrequent, whereas placebos are said to benefit 25 to 30 percent. If antidepressants were, indeed, so superior to placebos, this would be a persuasive advertisement for the biological approach.
We found 15 major reviews of the anti-depressant literature. Surprisingly, even the most positive reviews indicate that 30 to 40 percent of studies show no significant difference in response to drug versus placebo! The reviews indicate overall that one-third of patients do not improve with anti-depressant treatment, one-third improve with placebos, and an additional third show a response to medication they would not have attained with placebos. In the most optimistic view of such findings, two-thirds of the cases (placebo responders and those who do not respond to anything) do as well with placebo as with active medication.
We also found two large-scale quantitative evaluations (meta-analyses) integrating the outcomes of multiple studies of antidepressants. They clearly indicated, on the average, quite modest therapeutic power.
We were particularly impressed by the large variation in outcomes of studies conducted at multiple clinical sites or centers. Consider a study that compared the effectiveness of an antidepressant among patients at five different research centers. Although the pooled results demonstrate that the drug was generally more effective than placebo, the results from individual centers reveal much variation. After six weeks of treatment, every one of the six measures of effectiveness showed the anti-depressant (imipramine) to be merely equivalent to placebo in two or more of the centers. In two of the settings, a difference favoring the medication was detected on only one of 12 outcome comparisons.
In other words, the pooled, apparently favorable, outcome data conceal that dramatically different results could be obtained as a function of who conducted the study and the specific conditions at each locale. We can only conclude that a good deal of fragility characterized the apparent superiority of drug over placebo. The scientific literature is replete with analogous examples.
Incidentally, we also looked at whether modern studies, which are presumably better protected against bias, use higher doses, and often involve longer treatment periods, show a greater superiority of the antidepressant than did earlier studies. The literature frequently asserts that failures to demonstrate antidepressant superiority are due to such methodological failures as not using high enough doses, and so forth.
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