A client-level session-by-session evaluation of behavioral activation's mechanism of action

Our understanding of how Behavioral Activation (BA) for depression works is limited. BA is theorized to lead to changes in depression through changes in activation. While distal support for activation as a mechanism has been obtained, more research is needed before definitive conclusions can be drawn. Research on mechanism should consider the appropriate time-frame for examining changes in the theorized mechanism variable and whether the proposed mechanism is expected to exert causal influence in all BA cases. These issues were considered in the current study in which a post-hoc analysis was conducted to explore BA's mechanism using single-subject data obtained at each session during the course of treatment.

Activation and depression data were obtained from a randomized-controlled trial of BA for Latinos (BAL) compared to treatment-as-usual (TAU). Cross-lagged correlations were computed to test whether activation changes preceded, co-occurred with, or lagged behind changes in depression in a sample of 21 clients (BAL n = 14; TAU n = 7). Differences among participants based on activation-depression patterns were examined.

For 79% of the BAL sample, changes in activation preceded or co-occurred with changes in depression, while no clients in the TAU sample evidenced this pattern.

Use of more proximal and objective measures of the constructs of interest and a higher dosage of BA may have served as a stronger test of the treatment's mechanism.

More time-sensitive measurement of changes in variables of interest is needed.