Nutrition-focused group intervention with a strength-based counseling approach for people with clinical depression: a study protocol for the Food for Mind randomized controlled trial

BACKGROUND: Depression is a highly prevalent mental disorder with major public health effects globally. It impairs the quality of life and reduces the ability to work and function, leading to increasing costs of sick leaves and disability pensions. Current treatment strategies focus on biological and psychological pathways while understating the role of lifestyle factors. Epidemiological studies have shown convincing evidence of an inverse relationship between diet quality and depression. However, only limited data are available on the therapeutic effects of diet quality improvement on depression. Using a randomized controlled trial design, our primary aim is to investigate the effectiveness and cost-effectiveness of a behavioral nutrition group intervention compared to a social support intervention in the treatment of depression. METHODS: Participants (N=144, aged 20–65 years) with a diagnosis of moderate or severe depression recruited in collaboration with outpatient care units will be randomized into two arms: Food for Mind (FM) nutrition intervention (n=72) or Bring Good Mood (BGM) social support control group (n=72). Both arms will be provided with 6 group sessions over an 8-week period. FM involves improving diet quality by applying strength-based behavioral nutrition counseling and activities facilitated by a registered dietitian. The control arm comprises a befriending protocol. During the interventions, all participants will continue their treatment for depression as usual. Longitudinal data are collected at baseline, at 8 weeks, and at 6- and 12-month follow-ups. Depressive symptoms, diet quality, eating behavior, ability to work and function, and quality of life are assessed by self-reported questionnaires. A treatment expectancy questionnaire will be administered at baseline and an acceptability questionnaire at 8 weeks. The Center for Epidemiologic Studies Depression Scale is used as the primary endpoint at 1 year. The results will be analyzed with linear mixed-effects models. Economic evaluation includes both cost-effectiveness and cost-utility analysis. Two incremental cost-effectiveness ratios will be calculated to evaluate the incremental cost per QALY and the incremental cost per improvement in CES-D. DISCUSSION: If the intervention proves to be cost-effective and acceptable, it be can be implemented in healthcare to support the treatment of depression. TRIAL REGISTRATION: ClinicalTrials.gov NCT03904771. Retrospectively registered on 5 April 2019 SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13063-021-05279-5.