Intervention trial for workers with depressive symptoms

Depression is a major public health concern, because of its high prevalence, personal cost and suffering, and economic impact. A particular problem exists for depressed workers facing layoff and possible loss of health insurance. A structured 10-week intervention combining low-cost, self-directed therapies (specified doses of exercise and bright light exposure, and vitamin/omega-3 supplement) to improve mood and functioning in mild to moderately depressed factory workers was evaluated.

Method. A mixed method one-group repeated measures design included a non-random convenience sample of 18 female participants experiencing symptoms in the range of mild to moderate depression, all employees of a manufacturer experiencing layoffs. Measurement in the study included six instruments (Beck Depression Inventory-II (BDI-II), Work Productivity and Activity Impairment (WPAI), Rosenberg Self Esteem Scale (RSES), Psychological General Well-Being Schedule (PGWB), Pittsburg Sleep Quality Index (PSQI), and the Stroop Word-Color Task. Dependent variables were measured three times: baseline, week 5, and week 10. Repeated measures ANOVA was utilized for hypothesis testing. Qualitative data generation included narrative comments in daily Log Books, commentary during coaching phone calls every two weeks, a completion questionnaire and interview.

Findings. Participation in the intervention resulted in significant improvements in depression, work and activity impairment, general well-being, self-esteem, sleep quality and executive function (p = .00). Effect sizes were large, partial η2 = .597 for the Stroop Color-Word Task, .67 for the WPAI impairment at work, .71 for WPAI impairment in activities outside of work, .74 for the RSES, .88 for the PGWB, .89 for PSQI, and .97 for the BDI-II. Post-hoc testing included pairwise comparisons; all were significant from baseline to week 10, and all but one demonstrated significance between week 5 and week 10. Qualitative data confirmed quantitative findings, described change in areas not included as variables, and revealed description of changes over time and in time experience.

Conclusion. Tolerability and adherance was demonstrated for an intervention of self-directed therapies which resulted in significant improvements. Behavioral activation of the intervention had positive results on mood and sense of personal control and mastery. This is a shift from traditional care for with those with mild to moderate depression.