This approach utilizes accelerometry to measure NEA and electronic diaries for real-time psychological assessments, overcoming limitations of traditional methods such as retrospective bias and low ecological validity. Brief episodes of physical activity in daily life, which are distinctly different from structured exercise sessions, are generally linked to improved affective well-being. Notably, feelings of energy are particularly associated with incidental, unstructured, and non-exercise activities. Clinically, psychomotor retardation and diminished mood are key diagnostic features of MDD, with evidence suggesting that lower motor activity differentiates MDD patients from controls and that increased activity correlates with treatment response. In this context, the MASE project aims to design personalized BA interventions that focus on increasing NEA and, in turn, enhancing subjective energy levels to reduce depressive symptoms and prevent relapse.

Mental health problems are increasing worldwide. Major depressive disorder (MDD) is considered the worldwide leading source of disability. Therapeutic approaches are not fully understood and still improvable.

Behavioral activation (BA), a successful therapeutic approach for nearly 50 years, increases activation by means of establishing short, and rewarding experiences in patients' daily life, e.g., taking a shower. Current research clearly supports the effects of BA on MDD when comparing it to no intervention. However, BA alone is not superior to other specific forms of psychotherapy. To improve BA, it is necessary to better understand the behavioral and neurobiological underpinnings. Most recently, researchers identified a new potential starting point for treating MDD: the momentary relationship between physical activity and feelings of energy in everyday life. While past research focused on exercise for treating MDD, newer studies have found that not sports (e.g., jogging) but everyday physical activity (e.g., walking stairs) improves energy. The investigators call this relationship ASEA (real-life physical activity-subjective energy association), which describes how people feel more energized and awake when moving. Secondly, we determined a specific region in the brain for ASEA and its relationship to mental health. ASEA is important from a clinical perspective: Reductions in physical activity and loss of energy symptoms affect patients most and even individuals with a history of MDD show reduced physical activity. Short interventions in patients' daily life tackling ASEA are likely to improve MDD prevention and treatment. However, it is unclear who (e.g., patients with specific brain properties) benefits most from which intervention (type of nonexercise activity, timing, location, context). For example, people with a certain brain structure may especially profit from a short slow walk with others in the morning to increase energy and reduce depression while people with another certain brain area may benefit from fast stair-climbing in the evening. Therefore, the investigators aim to a) apply brain network analyses to identify types of brains likely to profit from ASEA, (b) use artificial intelligence to identify where and when nonexercise activity helps people with certain brain properties, (c) conduct an experimental study to test if the intervention suggestions found in step (a) and (b) really work out in everyday life and (d) develop and design a smartphone app that delivers ASEA interventions and provides suggestions when and where to engage in which short nonexercise activity to maximize participation rates. In sum, the aim is to advance scientifically proven interventions by unraveling the neurobiological aspects and to tailor interventions to individuals for prevention and treatment of MDD.

Inclusion Criteria:

• Sufficient knowledge of the German language
• Written informed consent.
• Score > 15 on the Montgomery Asberg Depression rating scale (MADRS) for MDD group.
• Remission within the past year and exhibit a MADRS score < 10 for at least one month for rMDD group

Exclusion Criteria:

• Pregnancy at baseline
• Claustrophobia
• Pacemaker
• Artificial heart valves
• Active implants
• Other psychiatric disorders
• Acute suicidality, change of medication / psychotherapy during the intervention (not dosage but substance).
• For healthy participants: history of any mental health condition or first-degree relative with affective / psychotic disorder

To facilitate data sharing, the investigators (Is) will include a standardized data request form and contact information for data requests in the MASE OSF folder. Pseudonymized processed data will be suitable for sharing with research organizations that will comply with the research project's data protection policy, GDPR and relevant ethical principles. In accordance with these policies, the Is will create a standardized data sharing agreement to be used by research organizations who wish to use the data for research purposes. The legal and ethical grounds for data sharing of pseudonymized data is consent of the participant. Raw location data will never be shared externally and will never leave UB and RUB. When sharing data, the Is will include a detailed codebook on all variables, defining their type, scale, content, and if applicable their calculation. The codebook will also contain information on the methodology of data collection and on all data preprocessing steps.

Embargo on collected data until the manuscripts on the main aims of the project are accepted for publication.

request form to PI (Prof. Markus Reichert)