Ecological Momentary Intervention for Reward in Anhedonia

Anhedonia, the diminished ability to experience positive emotions such as pleasure, is a clinically relevant condition central to depression and frequently observed across a range of other psychological disorders including anxiety disorders or chronic stress. Despite its prevalence and impact on quality of life, effective interventions specifically targeting anhedonia remain limited. Standard cognitive-behavioral therapies (CBT) often reduce negative affect (e.g., sadness, anxiety) but tend to be less effective in enhancing positive affect. Moreover, anhedonia has been proposed as a potential limiting factor in the efficacy of exposure-based treatments for anxiety disorders, underscoring the need for low-threshold interventions that directly target reward-related deficits.

At the core of anhedonia lies impaired reward processing, which involves multiple phases: (1) reward anticipation (wanting), (2) reward consumption (liking), and (3) reward-based learning. Individuals with elevated anhedonia often show deficits across these domains, leading to reduced engagement in rewarding activities and motivational impairments. Therefore, effective interventions should aim to strengthen these specific facets of reward functioning.

Emerging approaches such as Positive Affect Treatment (PAT) have demonstrated promising effects by combining components like positive mental imagery, savoring, self-reinforcement (i.e., taking ownership of positive experiences), and cognitive reframing (e.g., silver lining techniques). Complementary evidence suggests that gratitude-based interventions can enhance well-being and buffer against stress, based on the idea that gratitude and negative affect are partially incompatible.

Building on these findings, the current study tests a two-week ecological momentary intervention (EMI) designed to enhance reward processing and reduce anhedonia in daily life. The intervention is delivered via the smartphone app m-Path and comprises three brief training units per day. These include a combination of audio-guided exercises and ecological momentary assessments (EMA) capturing mood, activity, and psychological symptoms. The exercises target positive mental imagery, savoring, gratitude, silver lining, and taking ownership of positive experiences-each mapped onto distinct components of reward processing. EMI formats offer the advantage of flexibility and integration into everyday contexts without requiring direct clinician contact.

Participants are randomly assigned to either the reward-focused intervention group or an active control group. The control group receives a structurally equivalent two-week training consisting of progressive muscle relaxation (PMR) exercises, also delivered via the m-Path app. PMR is an established stress-reduction technique and serves as an active comparator matched in format, frequency, and duration. The control group completes two audio-guided PMR sessions per day and one brief reflection unit each evening.

It is hypothesized that the reward intervention will (a) reduce anhedonia and psychological distress more effectively than PMR and (b) lead to specific improvements in reward processing.

• Change in anhedonia; measured with the Dimensional Anhedonia Rating Scale (DARS) from baseline to completion and baseline to follow-up [Time frame: Baseline, 2 weeks (completion of intervention) and 3 months]
• Change in reward sensitivity and procession; measured with the Positive Valence System Scale-21 (PVSS-21) from baseline to completion and baseline to follow-up [Time frame: Baseline, 2 weeks (completion of intervention) and 3 months]
• Trait-Positive Emotionality (PE) and its change as measured with the NEO-Five-Factor (NEO-FFI) Positive-Emotionality-Subscale from baseline to completion and baseline to follow-up [Time frame: Baseline, 2 weeks (completion of intervention) and 3 months]
• Positive and negative affect and their changes; measured with the Positive and Negative Affect Schedule (PANAS) from baseline to completion and baseline to follow-up [Time frame: Baseline, 2 weeks (completion of intervention) and 3 months]
• Change in social anxiety; measured with the Social Phobia Inventory (SPIN) from baseline to completion and baseline to follow-up [Time frame: Baseline, 2 weeks (completion of intervention) and 3 months]
• Change in social anxiety; measured with the Social Interaction Anxiety Scale (SIAS) from baseline to completion and baseline to follow-up [Time frame: Baseline, 2 weeks (completion of intervention) and 3 months]
• Imagination abilities; measured with the Spontaneous Use of Imagery Scale (SUIS) from baseline to completion and baseline to follow-up [Time frame: Baseline, 2 weeks (completion of intervention) and 3 months]
• Vividness of mental images; measured with the Plymouth Sensory Imagery Questionnaire (PSI-Q) from baseline to completion and baseline to follow-up [Time frame: Baseline, 2 weeks (completion of intervention) and 3 months]
• Changes in feeling gratitude; measured with the Gratitude Questionnaire-Five-German (GQ-5-G) from baseline to completion and baseline to follow-up [Time frame: Baseline, 2 weeks (completion of intervention) and 3 months]
• Changes in perseverative thinking; measured with the Perseverative Thinking Questionnaire (PTQ) from baseline to completion and baseline to follow-up [Time frame: Baseline, 2 weeks (completion of intervention) and 3 months]
• Changes in use of emotion regulation strategies; measured with the Emotion Regulation Questionnaire (ERQ) from baseline to completion and baseline to follow-up [Time frame: Baseline, 2 weeks (completion of intervention) and 3 months]
• Changes in feeling overall relaxed (single self-composed visual analog scale item) from baseline to completion and baseline to follow-up [Time frame: Baseline, 2 weeks (completion of intervention) and 3 months]