Behavioral activation can normalize neural hypoactivation in subthreshold depression during a monetary incentive delay task.

Background: Late adolescents are under increased risk of developing depressive symptoms. Behavioral activation is an effective treatment for subthreshold depression, which can prevent the development of subthreshold depression into a major depressive disorder. However, the neural mechanisms underlying the efficacy of behavioral activation have not been clearly understood. We investigated neural responses during reward processing by individuals with subthreshold depression to clarify the neural mechanisms of behavioral activation.

Methods: Late adolescent university students with subthreshold depression (n=15, age 18-19 years) as indicated by a high score on the Beck's Depression Inventory-ll (BDI-ll) and 15 age-matched controls with a low BDI-ll score participated in functional magnetic resonance imaging scanning conducted during a monetary incentive delay task on two occasions. The Individuals in the subthreshold depression group received five, weekly behavioral activation sessions between the two scanning sessions. Moreover, they did not receive any medication until the study was completed.

Results: Behavioral activation significantly reduced depressive symptoms. Moreover, compared to the changes in brain functions in the control group, the behavioral activation group showed functional changes during loss anticipation in brain structures that mediates cognitive and emotional regulation, including the left ventrolateral prefrontal cortex and angular gyrus.

Limitations: Replication of the study with a larger sample size is required to increase the generalizability of these results.

Conclusions: Behavioral activation results in improved functioning of the fronto-parietal region during loss anticipation. These results increase our understanding of the mechanisms underlying specific psychotherapies.