Imager – An mHealth mental imagery-based ecological momentary intervention targeting reward sensitivity: A randomized controlled trial

Introduction: Robust sensitivity to reward may help preserve positive emotions in the face of adversity and has been proposed as a key resilience factor. We describe the development, feasibility, and efficacy of an mHealth application, Imager, which targets reward sensitivity by training individuals to create mental images of future rewarding experiences. Methods: We conducted a randomized controlled trial with healthy student participants screened for low reward sensitivity. Fifty-one participants in the intervention group (IG) received an ecological momentary intervention (EMI) - Imager, including 10 ecological momentary assessment (EMA) prompts per day over 7 days, of which three were combined with an instruction to engage in a mental imagery training. This part encouraged participants to create a mental image of a rewarding event. Forty-four participants from the control group (CG) received 10 EMA prompts per day, without the option of performing mental imagery training. Results: Adherence to Imager was high; participants in the IG engaged in 88.4% of the planned EMAs and EMIs. Intervention group participants reported fewer mental health symptoms, mainly in depression (=−0.34, df=93, p=0.004) and less perceived stress (=−0.18, df=93, p=0.035) than CG participants. There were no significant changes in self-reported reward sensitivity in the IG. Conclusions: Mental imagery training of future rewarding experiences was accepted by participants and integrated into their everyday lives. Our results show positive effects of Imager on mental well-being, although direct target engagement – self-reported reward sensitivity – was not confirmed. Prospective studies are needed to investigate the psychological, physiological, behavioral and neural mechanisms underlying Imager’s effects based on additional data on other populations.