Harmful Psychological Treatments

Psychotherapy Deterioration

Estimates of psychotherapy deterioration—that is, worsening of symptoms following psychotherapy—vary across controlled studies, but typically range from [Page 627]3% to 10%. In the substance abuse literature, estimates of deterioration have often been higher, averaging 10% to 15%. These percentages have led some researchers, such as Hans Strupp, Richard Stuart, and Scott Lilienfeld, to suggest that psychotherapy can in some cases be iatrogenic, that is, capable of causing harm.

Moreover, comprehensive meta-analyses (quantitative reviews) of the psychotherapy outcome literature have been reasonably consistent in revealing that control groups—groups that do not receive treatment—show higher end-state functioning than groups that receive treatment in a nontrivial minority of studies. A classic meta-analysis of psychotherapy outcome studies by Mary Lee Smith and Gene Glass found this to be true in 9% of the scientific investigations of the efficacy of psychotherapy. Later meta-analyses have reported similar or even higher percentages of negative outcomes. Even more troubling, meta-analyses of treatments for adolescent behavioral problems have suggested that as many as 29% of studies yield negative outcomes.

Troubling as they are, reported percentages of psychotherapy deterioration and negative effect sizes from meta-analyses are difficult to interpret. As the logical error of post hoc, ergo propter hoc (“after this, therefore because of this”) reminds us, deterioration following psychotherapy is not the same as deterioration resulting from psychotherapy. At least some of the deterioration reported in previous studies could reflect worsening due to extratherapy variables, such as stressful life events. Moreover, certain individuals who deteriorate following psychotherapy might have been even worse off had they not received psychotherapy. Therefore, estimates of psychotherapy deterioration, although suggestive of therapy-induced harm in some cases, cannot be interpreted directly as evidence for the negative effects of therapy.

The same holds for negative effect sizes from meta-analyses. Such effect sizes, especially if close to zero, could reflect random sampling error around a mean effect of zero. As a consequence, treatments that yield small negative effects could be merely inert rather than harmful per se. It should be noted, however, that inert treatments can cause harm indirectly by leading clients to forgo more efficacious therapies. Economists refer to this side effect as an opportunity cost, meaning that ineffective treatments may lead consumers to forfeit opportunities for successful treatment.

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