Cheshire
Senior Member (Voting Rights)
Abstract
The SMILES trial showed substantial improvement of depressive symptoms following seven consultations on healthy dieting. The very large effect size on depression reduction seems remarkable and we suggest that selectively induced expectancy and a loss of blinding have contributed to the observed effect.
Open access here.
Many similarities with the PACE flaws:
The primary outcome in the SMILES trial was change in the severity of depression symptoms, in this case assessed via the interviewer-rated Montgomery–Åsberg Depression Rating Scale (MADRS) [10]. Such outcomes are subjective in nature (the participant is queried about symptoms), and thus susceptible to expectancy effects (defined as results biased by the communication of the expected results [11, 12, 13, 14]). When the intervention is non-pharmacological – herein the advice of following a healthy diet – the blinding of conditions in an RCT is hardly possible. In order to minimize expectancy bias, the authors describe that they masked the hypothesis and used a neutral recruitment strategy. Participants were approached (in social media, local newspapers, and radio interviews) with the following message: “We are trialing the effect of an educational and counseling program focusing on diet that may help improve the symptoms of depression” ([1], p. 2). The paper further states that “several strategies were employed to reduce the risk of bias” ([1], p. 5) and that “significant effort was made to mask our hypothesis” ([1], p. 10).
In this letter, we argue that there is a mismatch between the reported and the actual recruitment strategy, which becomes clear when comparing the reported and actual recruitment strategies. Through a hyperlink to an external website on the study’s recruitment website [15] (note that there are some differences with current and previous versions), potential participants are presented to a ‘fruit smiley’, composed out of two green apples as eyes, a mandarin as nose, and a banana with the edges pointing up as a smiling mouth [16]. Messages such as: “Bananas look like a smile but can also help you smile because they contain tryptophan which is a mood stabilizer” and “Banana, brazil nuts, broccoli, they all have something in common apart from starting with the letter B. They all contain nutrients which can stabilize mood” are presented alongside. Since no benefits of the control conditioning (befriending) were described, we think that this is anything but a neutral description, which has likely affected expectancy in participants. The study hypothesis was provided at recruitment to potential participants ‘on a platter’, so to speak. Website visitors also learned that “the fear that we are eating our way to depression is prompting governments to take action” [15]. This was accompanied by testimonials, such as “The solution to my depression is good quality food”.In a local newspaper article entitled ‘Diet, Depression, Hope’ [17], published in the recruitment catchment area at time of enrolment, the senior author wrote “if you eat a healthier diet then it reduces your risk on depression”. This article was accompanied by an invitation to participate in the trial and contact details. In summary, the report of the SMILES trial does not seem to adequately describe how study recruitment took place in practice.