How to improve reward sensitivity - Predictors of long-term effects of a randomized controlled online intervention trial.

Background: Reward sensitivity is a central maintaining factor of depression. Current treatments fail at sufficiently and reliably modifying reward processing. Therefore, we employed interventions targeting reward sensitivity and evaluated the long-term efficacy of different online interventions, additionally exploring predictors of changes in reward sensitivity.

Methods: This four-arm randomized controlled trial (RCT) tested the long-term stability of treatment effects during a four-month follow-up in 127 participants of a two-week online intervention (behavioral activation vs. mindfulness and gratitude vs. combination of both). In addition, we investigated predictors of treatment success defined as improvement in reward sensitivity. Predictors we investigated were depressive expectations, stress and the type of reward implemented in the exercises of the intervention (physical activities and social encounters).

Results: The improvement concerning reward sensitivity, as well as the reduction of anhedonia and depressive symptoms was stable over a four-month follow-up. We did not find evidence for differences between the active intervention groups. Positive changes in depressive expectations were a significant predictor of long-term improvements in reward sensitivity.

Limitations: Only self-report measures were used and the interpretation of the long-term efficacy of the online interventions is limited since the waitlist control condition was not extended to the follow-up.

Conclusions: Clinicians should focus on violating depressive expectations to facilitate updating the prediction and anticipation of future rewarding experiences. This could be a vital mechanism of change in reward sensitivity. However, future research still needs to unravel what kind of interventions are most effective in targeting reward insensitivity.