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Table 1 Summary of trial characteristics

From: Placebo response and effect in randomized clinical trials: meta-research with focus on contextual effects

Characteristic Trials (k = 186)
Number of patients 16,655
Proportion of women (SD) 58.6 (28.6)
Mean age, years (SD) 39.9 (17.1)
Condition
 Abortion, n (%) 3 (1.6)
 Anxiety, n (%) 3 (1.6)
 Asthma, n (%) 3 (1.6)
 Cancer, n (%) 5 (2.9)
 Dementia, n (%) 3 (1.6)
 Depression, n (%) 9 (4.8)
 Fibromyalgia, n (%) 3 (1.6)
 Headache, n (%) 8 (4.3)
 Hypertension, n (%) 7 (3.8)
 Insomnia, n (%) 5 (2.9)
 Low back pain, n (%) 3 (1.6)
 Obesity, n (%) 8 (4.3)
 Osteoarthritis, n (%) 5 (2.9)
 Phobia, n (%) 3 (1.6)
 Schizophrenia, n (%) 3 (1.6)
 Smoking, n (%) 9 (4.8)
 Surgery/procedure, n (%) 45 (24.2)
 Othera, n (%) 61 (32.8)
No. center
 Single, n (%) 97 (52.1)
 Unclear, n (%) 56 (30.1)
 Multi, n (%) 33 (17.7)
Type of intervention
 Psychological, n (%) 62 (33.3)
 Pharmacological, n (%) 56 (30.1)
 Physical, n (%) 68 (36.6)
Study duration
 < 4 weeks, n (%) 83 (44.6)
 4 to 8 weeks, n (%) 44 (23.7)
 8 to 12 weeks, n (%) 27 (14.5)
 > 12 weeks, n (%) 32 (17.2)
Outcome domain
 Anxiety, n (%) 9 (4.8)
 Depression, n (%) 10 (5.4)
 Diastolic blood pressure, n (%) 7 (3.8)
 Medication use, n (%) 9 (4.8)
 Nausea, n (%) 9 (4.8)
 Pain, n (%) 53 (28.5)
 Sleep disturbance, n (%) 6 (3.2)
 Smoking cessation, n (%) 9 (4.8)
 Weight, n (%) 8 (4.3)
 Otherb, n (%) 66 (35.5)
High risk, n (%) 170 (91.4)
  1. aConditions investigated in less than three trials, bOutcomes reported in less than three trials