Study Design and Number of Studies and Participantsb
N = number of studies. RCT = randomized controlled trial; NRS = nonrandomized comparison study;
OBS = observational study,
1980-2009. Language: 8 in Chinese and 32 in English.
Study site: United States (n = 20); China (n = 11); Australia (n = 6); United Kingdom (n = 1); Germany (n = 1); France (n = 1). Most studies assessed more than one psychological well-being state (the numbers add up to more than 40.)
RCT (N = 17): The investigator manipulates use of the procedure by offering it to one group of people (the exposed group), and offering nothing, a placebo, or some other procedure (s) to another group (the control group) by random allocation. Both groups are then followed to observe the rates of various outcomes.
NRS (N = 16 before and after trials and 2 external comparisons): The investigator causes some subjects to be exposed to the procedure, but does not use random allocation to determine the exposure that includes both an "internal comparison (before and after)" and an "external comparison (unexposed group)."
OBS (N = 7, cross-sectional nature): The investigator does not manipulate use of the procedure, but merely observes and interprets the outcomes.