PsycINFO does not index randomized controlled trials at all, and thus its important to use other thesaurus terms and add free text words for searching1.
Identifying RCTs in PsycINFO2. Search strategy, amended to ProQuest format
SU.EXACT("Treatment Effectiveness Evaluation") OR SU.EXACT.EXPLODE("Treatment Outcomes") OR SU.EXACT("Placebo") OR SU.EXACT("Followup Studies") OR placebo* OR random* OR "comparative stud*" OR clinical NEAR/3 trial* OR research NEAR/3 design OR evaluat* NEAR/3 stud* OR prospectiv* NEAR/3 stud* OR (singl* OR doubl* OR trebl* OR tripl*) NEAR/3 (blind* OR mask*)
Strategies for finding methodologically sound therapy studies in PsycInfo1, amended to ProQuest format
Best sensitivity:
random* OR control* OR SU.EXACT.EXPLODE(treatment)
Best optimization of sensitivity and specificity:
"double-blind" OR "random* assigned" OR control
1. Eady AM, Wilczynski NL, Haynes RB. PsycINFO search strategies identified methodologically sound therapy studies and review articles for use by clinicians and researchers. Journal of Clinical Epidemiology. 2008 Jan;61(1):34-40
2. Watson RJ, Richardson PH. Identifying randomized controlled trials of cognitive therapy for depression: comparing the efficiency of Embase, Medline and PsycINFO bibliographic databases. Br J Med Psychol. 1999 Dec;72 ( Pt 4):535-42