Not All Masks Are Created Equal: Masking Success in Clinical Trials of Children and Adolescents.

The current study assessed the success of masking omega-3 (Ω3) and psychotherapy in clinical trials of youth with depression or bipolar spectrum disorder. Participants were youth ages 7-14 with DSM-IV-TR diagnosed depressive (n = 72) or bipolar spectrum (n = 23) disorders. Inclusion diagnoses were depressive disorder, cyclothymic disorder, or bipolar disorder not otherwise specified. Exclusion diagnoses included bipolar I or II disorder, chronic medical condition or autism. Youth participated in 2 × 2 randomized controlled trials, in which they received Ω3 or placebo (PBO) and psychoeducational psychotherapy (PEP) or active monitoring (AM). Participants and study staff (including independent interviewers) were masked to Ω3/PBO allocation. Besides the masked independent interviewers, one coprincipal investigator (Co-PI) was fully masked to both conditions and completed all consensus conference ratings postrandomization. At the endpoint assessment or last completed interview, interviewers and the masked Co-PI guessed whether each child was assigned to Ω3 or PBO and to PEP or AM. Masking failure was calculated using the degree of correct guesses above chance level using binomial tests across all participants for Ω3 versus PBO and PEP versus AM. For all guessers, Ω3 allocation was guessed correctly approximately half the time (50%-52.5%). Rates of correct guessing were higher for PEP, but only the interviewer guesses were correct significantly more often (58.5%-68.7%) than chance. Reporting of masking success should be an essential element of RCTs. Psychotherapy is generally more difficult to mask, but with attentive masking procedures reasonable masking can be achieved.