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Table 1 Overview of included studies.

From: Frequency and circumstances of placebo use in clinical practice - a systematic review of empirical studies

First author year from N Participants Sampling Response rate Focus pure/impure placebo
Questionnaire-based quantitative surveys       
Shapiro 1973 [15, 16] USA 195 Ph (various groups) Convenience 83% Both
Goldberg 1979 [18] USA 102 N (head nurses at 11 hospitals) Local 68% Pure
Goodwin 1979 [19] USA 60 Ph (house officers) Convenience 100% Mainly
   39 N (hospital nurses) Convenience Unclear pure
   27 License practical nurses/medical aides Convenience Unclear  
Gray 1981 [20] CAN 70 Ph (university hospital) Convenience 82%* Pure
   230 N (university hospital) Convenience   
   35 N (experienced hospital nurses) Convenience Unclear  
Lange 1981 [21] GER 81 Ph, N, psychologists (no data for subgroups provided) Convenience Unclear Pure
Thomson 1982 [22] NZ 37 Ph (GPs) Local 84% Both
Classen 1985 [23] GER 101 Ph (setting unclear) Convenience Unclear Both
Saupe 1986 [24] GER 56 N (at a psychiatric university hospital) Convenience 80% Mainly pure
Lynöe 1993 [26] SWE 94 Ph (GPs or affiliated with university) Local 94% Mainly
   83 Pt (consecutive patients of three GPs) Local 83% impure
Ernst 1997 [27] AUS 263 N (setting unclear) Convenience 58% Both
Berger 1999 [28] USA 74 Medical interns at an university-affiliated hospital Convenience 83% Pure
Berthelot 2001 [29] FRA 300 Pt (at a hospital rheumatology department) Convenience Unclear Mainly
   100 N (same hospital, various departments) Convenience Unclear pure
Hrobjartsson 2003 [30] DEN 502 Ph (GPs, hospital, specialists in private practice) Random 65% Both
Nitzan 2005 [31] ISR 31 Ph (senior hospital physicians) Convenience 76% Mainly
   31 N (head nurses from same hospitals) Convenience 100% pure
   27 Ph (family physicians) Convenience 68%  
Lim 2007 [32] SIN 402 Medical students Local 36% Pure
Sherman 2007 [33] USA 231 Ph (faculty members of 3 medical schools) Local 50% Both
Tilburt 2008 [34] USA 679 Ph (internists and rheumatologists) Random 57% Both
Bernateck 2009 [35] GER 71 Ph (university hospital) Convenience 80%* Pure
   107 N (university hospital) Convenience   
Chen 2009 [36] NZ 211 Pt (in waiting rooms of two GP clinics) Convenience 48% Mainly pure
Fässler 2009 [37] SWI 233 Ph (primary care) Random 48% Both
Substudies with prospective screening of medical records of hospital patients       
Goodwin 1979 [19] USA 1900 Pt (academic teaching hospital, treated during 6 months) n.a.   Pure
Lange 1981 [21] GER 1725 Pt (psychiatric hospital, all treated 1978) n.a.   Pure
Qualitative studies       
Comaroff 1976 [17] UK 47 Ph (GPs) Local 92% Mainly impure
Schwartz 1989 [25] USA 72 Ph (selected for often prescribing inefficient drugs) n.a. 51% Impure
  1. *Response rate only reported for pooled groups.
  2. Ph = physicians; N = nurses; Pt = patients; GPs = general practitioners; n.a. = not applicable.
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