Mean effect sizes for changes in depression were calculated for 2,318 patients who had been rando... more Mean effect sizes for changes in depression were calculated for 2,318 patients who had been randomly assigned to either antidepressant medication or placebo in 19 double-blind clinical trials. As a proportion of the drug response, the placebo response was constant across different types of medication (75%), and the correlation between placebo effect and drug effect was .90. These data indicate that virtually all of the variation in drug effect size was due to the placebo characteristics of the studies. The effect size for active medications that are not regarded to be antidepressants was as large as that for those classified as antidepressants, and in both cases, the inactive placebos produced improvement that was 75% of the effect of the active drug. These data raise the possibility that the apparent drug effect (25% of the drug response) is actually an active placebo effect. Examination of pre-post effect sizes among depressed individuals assigned to no-treatment or wait-list control groups suggest that approximately one quarter of the drug response is due to the administration of an active medication, one half is a placebo effect, and the remaining quarter is due to other nonspecific factors.
Journal of Consulting and Clinical Psychology, 1995
A meta-analysis was performed on 18 studies in which a cognitive-behavioral therapy was compared ... more A meta-analysis was performed on 18 studies in which a cognitive-behavioral therapy was compared with the same therapy supplemented by hypnosis. The results indicated that the addition of hypnosis substantially enhanced treatment outcome, so that the average client receiving cognitive-behavioral hypnotherapy showed greater improvement than at least 70% of clients receiving nonhypnotic treatment. Effects seemed particularly pronounced for treatments of obesity, especially at long-term follow-up, indicating that unlike those in nonhypnotic treatment, clients to whom hypnotic inductions had been administered continued to lose weight after treatment ended. These results were particularly striking because of the few procedural differences between the hypnotic and nonhypnotic treatments.
Placebo analgesia was produced by conditioning trials wherein heat induced experimental pain was ... more Placebo analgesia was produced by conditioning trials wherein heat induced experimental pain was surreptitiously reduced in order to test psychological factors of expectancy and desire for pain reduction as possible mediators of placebo analgesia. The magnitudes of placebo effects were assessed after these conditioning trials and during trials wherein stimulus intensities were reestablished to original baseline levels. In addition, analyses were made of the in¯uence of these psychological factors on concurrently assessed pain and remembered pain intensities. Statistically reliable placebo effects on sensory and affective measures of pain were graded according to the extent of surreptitious lowering of stimulus strength during the manipulation trials, consistent with conditioning. However, all of these effects were strongly associated with expectancy but not desire for relief. These results show that although conditioning may be suf®cient for placebo analgesia, it is likely to be mediated by expectancy. The results further demonstrated that placebo effects based on remembered pain were 3 to 4 times greater than those based on concurrently assessed placebo effects, primarily because baseline pain was remembered as being much more intense than it actually was. However, similar to concurrent placebo effects, remembered placebo effects were strongly associated with expected pain levels that occurred just after conditioning. Taken together, these results suggest that magnitudes of placebo effect are dependent on multiple factors, including conditioning, expectancy, and whether analgesia is assessed concurrently or retrospectively. q 1999 International Association for the Study of Pain. Published by Elsevier Science B.V.
Journal of Consulting and Clinical Psychology, 1995
A meta-analysis was performed on 18 studies in which a cognitive-behavioral therapy was compared ... more A meta-analysis was performed on 18 studies in which a cognitive-behavioral therapy was compared with the same therapy supplemented by hypnosis. The results indicated that the addition of hypnosis substantially enhanced treatment outcome, so that the average client receiving cognitive-behavioral hypnotherapy showed greater improvement than at least 70% of clients receiving nonhypnotic treatment. Effects seemed particularly pronounced for treatments of obesity, especially at long-term follow-up, indicating that unlike those in nonhypnotic treatment, clients to whom hypnotic inductions had been administered continued to lose weight after treatment ended. These results were particularly striking because of the few procedural differences between the hypnotic and nonhypnotic treatments.
Mean effect sizes for changes in depression were calculated for 2,318 patients who had been rando... more Mean effect sizes for changes in depression were calculated for 2,318 patients who had been randomly assigned to either antidepressant medication or placebo in 19 double-blind clinical trials. As a proportion of the drug response, the placebo response was constant across different types of medication (75%), and the correlation between placebo effect and drug effect was .90. These data indicate that virtually all of the variation in drug effect size was due to the placebo characteristics of the studies. The effect size for active medications that are not regarded to be antidepressants was as large as that for those classified as antidepressants, and in both cases, the inactive placebos produced improvement that was 75% of the effect of the active drug. These data raise the possibility that the apparent drug effect (25% of the drug response) is actually an active placebo effect. Examination of pre-post effect sizes among depressed individuals assigned to no-treatment or wait-list control groups suggest that approximately one quarter of the drug response is due to the administration of an active medication, one half is a placebo effect, and the remaining quarter is due to other nonspecific factors.
Mean effect sizes for changes in depression were calculated for 2,318 patients who had been rando... more Mean effect sizes for changes in depression were calculated for 2,318 patients who had been randomly assigned to either antidepressant medication or placebo in 19 double-blind clinical trials. As a proportion of the drug response, the placebo response was constant across different types of medication (75%), and the correlation between placebo effect and drug effect was .90. These data indicate that virtually all of the variation in drug effect size was due to the placebo characteristics of the studies. The effect size for active medications that are not regarded to be antidepressants was as large as that for those classified as antidepressants, and in both cases, the inactive placebos produced improvement that was 75% of the effect of the active drug. These data raise the possibility that the apparent drug effect (25% of the drug response) is actually an active placebo effect. Examination of pre-post effect sizes among depressed individuals assigned to no-treatment or wait-list control groups suggest that approximately one quarter of the drug response is due to the administration of an active medication, one half is a placebo effect, and the remaining quarter is due to other nonspecific factors.
Journal of Consulting and Clinical Psychology, 1995
A meta-analysis was performed on 18 studies in which a cognitive-behavioral therapy was compared ... more A meta-analysis was performed on 18 studies in which a cognitive-behavioral therapy was compared with the same therapy supplemented by hypnosis. The results indicated that the addition of hypnosis substantially enhanced treatment outcome, so that the average client receiving cognitive-behavioral hypnotherapy showed greater improvement than at least 70% of clients receiving nonhypnotic treatment. Effects seemed particularly pronounced for treatments of obesity, especially at long-term follow-up, indicating that unlike those in nonhypnotic treatment, clients to whom hypnotic inductions had been administered continued to lose weight after treatment ended. These results were particularly striking because of the few procedural differences between the hypnotic and nonhypnotic treatments.
Placebo analgesia was produced by conditioning trials wherein heat induced experimental pain was ... more Placebo analgesia was produced by conditioning trials wherein heat induced experimental pain was surreptitiously reduced in order to test psychological factors of expectancy and desire for pain reduction as possible mediators of placebo analgesia. The magnitudes of placebo effects were assessed after these conditioning trials and during trials wherein stimulus intensities were reestablished to original baseline levels. In addition, analyses were made of the in¯uence of these psychological factors on concurrently assessed pain and remembered pain intensities. Statistically reliable placebo effects on sensory and affective measures of pain were graded according to the extent of surreptitious lowering of stimulus strength during the manipulation trials, consistent with conditioning. However, all of these effects were strongly associated with expectancy but not desire for relief. These results show that although conditioning may be suf®cient for placebo analgesia, it is likely to be mediated by expectancy. The results further demonstrated that placebo effects based on remembered pain were 3 to 4 times greater than those based on concurrently assessed placebo effects, primarily because baseline pain was remembered as being much more intense than it actually was. However, similar to concurrent placebo effects, remembered placebo effects were strongly associated with expected pain levels that occurred just after conditioning. Taken together, these results suggest that magnitudes of placebo effect are dependent on multiple factors, including conditioning, expectancy, and whether analgesia is assessed concurrently or retrospectively. q 1999 International Association for the Study of Pain. Published by Elsevier Science B.V.
Journal of Consulting and Clinical Psychology, 1995
A meta-analysis was performed on 18 studies in which a cognitive-behavioral therapy was compared ... more A meta-analysis was performed on 18 studies in which a cognitive-behavioral therapy was compared with the same therapy supplemented by hypnosis. The results indicated that the addition of hypnosis substantially enhanced treatment outcome, so that the average client receiving cognitive-behavioral hypnotherapy showed greater improvement than at least 70% of clients receiving nonhypnotic treatment. Effects seemed particularly pronounced for treatments of obesity, especially at long-term follow-up, indicating that unlike those in nonhypnotic treatment, clients to whom hypnotic inductions had been administered continued to lose weight after treatment ended. These results were particularly striking because of the few procedural differences between the hypnotic and nonhypnotic treatments.
Mean effect sizes for changes in depression were calculated for 2,318 patients who had been rando... more Mean effect sizes for changes in depression were calculated for 2,318 patients who had been randomly assigned to either antidepressant medication or placebo in 19 double-blind clinical trials. As a proportion of the drug response, the placebo response was constant across different types of medication (75%), and the correlation between placebo effect and drug effect was .90. These data indicate that virtually all of the variation in drug effect size was due to the placebo characteristics of the studies. The effect size for active medications that are not regarded to be antidepressants was as large as that for those classified as antidepressants, and in both cases, the inactive placebos produced improvement that was 75% of the effect of the active drug. These data raise the possibility that the apparent drug effect (25% of the drug response) is actually an active placebo effect. Examination of pre-post effect sizes among depressed individuals assigned to no-treatment or wait-list control groups suggest that approximately one quarter of the drug response is due to the administration of an active medication, one half is a placebo effect, and the remaining quarter is due to other nonspecific factors.
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