Searches through databases and review articles located 7605 records (Fig. 1). After removing 2351 duplicated records or records before January 1, 1990, 3656 irrelevant titles, and 675 ineligible abstracts, 923 articles were retained for full-text review. Of them, 894 were eliminated for not fulfilling one of the criteria. Thus, 29 studies were included for outcome-level analysis. Eight studies without an inactive control or minimum intervention were excluded; 21 studies were retained for study-level meta-analysis.
Descriptive results. Of the 29 studies, 21 studies compared efficacies between interventions and inactive or minimal controls, yielding 25 comparisons in the study-level meta-analysis. Two studies adopted pharmacological treatments alone; 16 employed non-pharmacological interventions; 8 used multimodal interventions. Two studies adopted both non-pharmacological and multimodal interventions; and one study employed both pharmacological and multimodal interventions. The majority of the trials were conducted in the U.S. (n = 17); the rest (n = 12) came from other countries with distinct demographic features.