General medicine Psychiatry Type of intervention* Pharmacological 83 89 Surgical 0 0 Behavioural 1 2 Device 0 3 Physiotherapeutic 3 0 Nutritional supplement 9 0 Other 4 3 Total 100 97 Type of placebo Not reported 16 38 Capsule 18 28 Tablet 20 16 Injection 23 5 Sham device 2 1 Sham procedure 2 0 Oral solution 9 3 Inhaler 2 0 Other 9 3 Total 101 94

^* 3 trials in general medicine and 3 trials in psychiatry had more than one intervention.

4 trials in general medicine and 1 trial in psychiatry had more than one type of placebo.