Efficacy and mechanism of activity scheduling with positive imagery for behavioural activation in subclinical depression: A randomized controlled trial.

BACKGROUND

Like major depressive disorder, subclinical depression involves reduced interest or pleasure in activities. Preliminary evidence suggests imagery-based episodic simulation of planned activities boosts motivation and engagement, but its effects and underlying mechanisms in individuals with subclinical depression remain unclear.

METHODS

This prospectively registered randomized controlled trial (Registration No.: ChiCTR2400084768) adopted a single-blind design. A total of, 203 subclinically depressed participants were randomly assigned via computer-generated random number list to the activity scheduling with positive imagery (ASI) group (n = 68), activity scheduling (AS) group (n = 67) or wait-list (WL) group (n = 68). Assessments at pre-treatment, post-treatment and 2-month follow-up measured primary outcomes (behavioural activation, depressive symptoms, prospective imagery) and the secondary outcome (activity ratings).

RESULTS

At post-treatment, the ASI group had increased behavioural activation (d = 0.69-0.99), alleviated depressive symptoms (d = 1.03-1.16), enhanced positive prospective imagery (d = 1.74-2.16) and reduced negative prospective imagery (d = 0.31-0.59) compared to the AS and WL groups. At follow-up, the ASI group outperformed the WL group in depressive symptom improvement (d = 1.32) and behavioural activation (d = 0.51). Additionally, the ASI group demonstrated significantly greater enhancements in anticipated pleasure and anticipated reward for enjoyable activities than the AS group post-training. Exploratory mediation analyses suggested that ASI training may promote behavioural activation and alleviate depressive symptoms by enhancing positive (rather than reducing negative) prospective imagery.

CONCLUSIONS

The ASI was an appropriate intervention for subclinical depression. Enhanced positive prospective imagery may be a potential mechanism in ASI training, requiring large-sample validation.