Effects and moderators of a 16-week intervention on contextual physical activity in adults with moderate to severe depressive symptoms: short and long-term results of a randomized clinical trial.

Background: Depression is associated with reduced physical activity (PA), and evidence on the long-term effects of interventions and their potential moderators remains limited. Thus, this study aimed to evaluate the short- (post-intervention) and long-term (six-month follow-up) effects of a PA-promoting intervention on contextual PA and to explore potential moderators in adults with depressive symptoms.

Methods: A randomized, controlled, and assessor-blinded clinical trial was conducted with adults presenting depressive symptoms. The intervention lasted 16 weeks, with two sessions per week. Strategies were grounded in Self-Determination Theory and aimed to increase participants' awareness of their lifestyle, primarily focusing on PA and its relationship with depression. Activities included lectures, group discussions, interactive activities with family and friends, and PA practices in different contexts. Intensity-specific PA was assessed using wrist-worn accelerometers, and contextual PA (by type and domain) was self-reported. Generalized estimating equations were used to assess intervention effects. Potential moderators (sex and age) were examined in exploratory analyses using three-way interaction terms.

Results: A total of 78 individuals (76.9% women, mean age 37.5 ± 10.2) were equally randomized into control (CG) and intervention (IG) groups. No significant group-by-time interactions were identified in the intention-to-treat analyses. However, per-protocol analysis suggested that the intervention increased leisure-time PA compared to controls (p = 0.004), with short-term increases (between-group changes of 119.6 min/week) and maintenance at follow-up (83.6 min/week). Exploratory moderator analyses indicated potential differences in intervention effects according to sex and age.

Conclusion: Although no significant effects were identified in the intention-to-treat analyses, per-protocol findings suggested potential increases in leisure-time PA among participants with higher adherence. Exploratory findings indicate possible variation according to sex and age, but these results should be interpreted with caution and considered hypothesis-generating. Overall, the findings highlight the importance of strategies to improve adherence in PA interventions targeting adults with depressive symptoms.

Trial registration: Brazilian Registry of Clinical Trials (ReBEC) RBR7466htj, April, 17 2023. Retrospectively registered.