Evidence for placebo effects on physical but not on biochemical outcome parameters: a review of clinical trials

Table 1 Reasons for exclusion and number of excluded trials during the selection process of the first dataset

Reasons for exclusion	n
Lack of placebo-controlled, double-blind, randomized trial
Review, article, or comment	272
No placebo used	186
Lack of double-blinding or randomization	96
Kind of investigated symptom or condition
No clinical condition	44
Psychological, neurological or psychiatric condition	106
Subjective symptom	67
No classic placebo control group
Placebo as a dummy to maintain blinding of experimental treatments	147
Placebo as a control of an add-on treatment	74
Lack of stable disease condition
Medical intervention preceding experimental treatment	120
Co-medication changed during study	33
Acute condition	79
Developmental disorder	20
Trial focus on relapse or prevention	131
Trial focus on death or other serious events	113
Trial focus on long-term development of disease	121
Miscellaneous
Crossover design and results not separated by sequence	23
Native physiological parameter not reported	17
Insufficient detail to estimate placebo effect	40
Total	1689

ISSN: 1741-7015