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As the blind folds.

Studies of psychotherapy and psychiatric drugs aim for a double-blind design, one in which neither people getting treatment nor clinicians gauging responses to treatment can consistently distinguish between a genuine intervention and a placebo. The latter may consist of a sugar pill or sessions with a physician not designed to offer specific psychological help.

However, a new report suggests that clinicians participating in such studies often correctly guess the treatment status of participants, possibly leading to inflated estimates of how well psychotherapy and psychiatric drugs work.

"The effectiveness and significance of blinding procedures have been unduly ignored in psychotherapy research," assert Kathleen M. Carroll, a psychologist at Yale University School of Medicine, and her colleagues. Evidence already exists that volunteers and investigators frequently figure out who is getting a genuine drug and who is receiving a placebo, they note, because of the absence of side effects in people taking placebos. The impact of accurate guessing on treatment ratings for antidepressants and other psychoactive drugs remains controversial (SN: 10/10/92, p.231).

Carroll and her coworkers studied 73 cocaine abusers for 1 to 3 months. Volunteers randomly entered one of four treatment groups: psychotherapy focused on strategies to prevent relapse plus an antidepressant drug (desipramine); psychotherapy plus placebo pills; general support and medical monitoring (placebo psychotherapy) plus desipramine; and placebo psychotherapy plus placebo pills.

Reduction in cocaine use and other improvements occurred about equally in all four groups. The most severe abusers benefited more from relapse therapy than support; less severe abusers did better with desipramine than placebo pills.

When treatment ended, two clinicians involved in the study correctly guessed volunteers' psychotherapy and drug treatment status in three-quarters of the cases, Carroll's group reports in the April JOURNAL OF CONSULTING AND CLINICAL PSYCHOLOGY. These clinicians rated active treatments as substantially more effective when they had accurately guessed that a participant was receiving one or both of them.

Investigators should work to maintain "blind" treatment and placebo groups, the scientists argue.
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Title Annotation:double-blind procedures in psychotherapy and psychiatric drug research often ineffective
Publication:Science News
Date:May 21, 1994
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