Evaluating cognitive effort in a randomized controlled trial.

Many randomized controlled trials (RCTs) of neuropsychiatric conditions involve cognitive outcome measures; however, validity of cognitive data relies on adequate effort during testing, and such screening is seldom performed. Given well-established rates of 10 to 30% poor effort in clinical settings, this is not a trivial concern. This preliminary study evaluated effort during cognitive testing in an RCT of omega-3 supplementation to reduce suicidality in a high-risk psychiatric population. An interim analysis of sustained attentions measures from the Connors Performance Test (CPT-2) at baseline for the first 60 participants was conducted. Previously validated cut points to detect insufficient effort on the CPT-2 were applied. At baseline, 12% (7) were identified as giving poor effort. Follow-up analyses indicated less psychiatric distress and suicidality among those who gave poor effort. Results suggest comparable likelihood of a poor effort on cognitive testing in clinical and RCT participation. Reduced psychiatric distress in the poor effort group raises concern regarding interpretation of other measures. The importance of screening cognitive data for effort in RCTs is highlighted. Future studies will examine effort at follow-up visits, and explore relationships to attrition, adherence, and response to treatment. Copyright © 2016 John Wiley & Sons, Ltd.