Lifestyle physical activity coaching in outpatients with major depressive disorder (PACOUTPAT): study protocol for a randomized controlled trial on physical activity, depression, and quality of life.

Physical activity has been shown to reduce depressive symptoms to a similar extent as antidepressant medication.

• This is cited as existing evidence motivating the intervention study.
• Despite this evidence, individuals with MDD engage in lower levels of PA and exhibit higher levels of sedentary behavior.
• Structural, physical, and psychological barriers hinder PA engagement in this population.

The trial uses a three-arm randomized controlled trial design conducted at a psychiatric day clinic in German-speaking Switzerland.

• A total of 114 individuals aged 18 to 65 years with a clinical diagnosis of MDD (ICD-10: F32 and F33) are recruited on an ongoing basis.
• Participants are randomly assigned to one of three groups.
• The study is registered under DRKS00036209, registered on 08 May 2025.

The three study arms include a 10-week PA coaching program with wearable support, the same program extended by a remote 26-week cognition-based coaching phase, and a control group receiving treatment as usual with written PA guidelines.

• Group 1: A 10-week PA coaching program based on interest and experience in PA, supported by a wearable smart ring for self-monitoring.
• Group 2: The same 10-week program extended by an additional, remote 26-week cognition-based coaching phase.
• Group 3: A control group receiving treatment as usual along with written current PA guidelines.
• The intervention combines affective with cognitive components of behavior change.

Data is collected at three measurement timepoints across the study duration.

• Baseline measurement is taken 2–4 weeks after the start of day clinic treatment.
• Post measurement is taken after the 10-week coaching phase.
• Follow-up measurement is taken after a 6-month follow-up period.

The primary outcome is device-measured physical activity change over time, measured via Fibion® accelerometer and analyzed using linear mixed models.

• PA is measured at baseline, post, and follow-up timepoints.
• The Fibion® accelerometer is used for objective measurement.
• Linear mixed models are specified as the primary analytic approach.
• Secondary outcomes include depression severity and quality of life.

The intervention is designed to address affective responses to PA in addition to cognitive behavior change strategies, with technology-based self-monitoring support via a wearable smart ring.

• Previous research is cited as highlighting the importance of addressing affective responses to PA in interventions.
• The support of technology-based tools, such as wearables, is described as 'promising.'
• Potential mechanisms of behavior change and participant experiences are also examined as part of the study.