Table 1 Medline search strategy

001 controlled clinical trials/

002 randomized controlled trials/

003 exp research design/

004 multi-center studies/

005 single-blind method/

006 clinical trial.pt.

007 ((single or double or treble or triple) adj5 (mask$ or blind)).tw.

008 placebos/or placebo$.tw.

009 or/1–8

010 depress$.mp. [mp = title, original title, abstract, name of substance word, subject heading word]

011 (family practi$ or general practi$ or primary care$ or family physician$).mp. [mp = title, original title, abstract, name of substance word, subject heading word]

012 9 and 10 and 11