It is well known that physical activity interventions have a robust, if small-to-moderate effect on the amelioration of chronic diseases, including major depressive disorder (MDD) (Singh et al. 2023). At the same time, behavioral activation is one of the most effective components of digital cognitive-behavioral therapy for depression (Furakawa et al. 2021). Here we leveraged smartwatches to provide an interactive tool for delivering a mixed intervention of physical and behavioral activation, with the former addressing physical activity level and the latter pleasant activities including and beyond physical activity (e.g., social, relaxing activities). Moreover, given the relationship with physical activity level, we additionally incorporated digital insomnia exercises that have also shown promising effects in the amelioration of depression. Our primary aim was to estimate the effects of our digital smartwatch-based intervention in a small sample of depressed patients.

Inclusion Criteria:

• Written consent for voluntary study participation
• Between 18 and 65 years of age
• Current diagnosis of a single episode of mild to moderate depressive disorder without psychotic symptoms, according to ICD-10 (F32.0, F32.1)
• Internet access and email address to answer electronic questionnaires
• Ability to read German

Exclusion Criteria:

• Acute suicidality
• Pregnancy and breastfeeding
• Currently undergoing psychological treatment
• Current use of psychotropic medication
• Neurological or internal medical disease
• Diagnosis of a severe major depression or dysthymia according to ICD-10 (F32.2, F32.3, F33.2, F33.3, F34.1)
• Diagnosis of a psychotic disorder according to ICD-10 (F20-F29) in the life history
• Diagnosis of a bipolar disorder according to ICD-10 (F31) in life history
• Acute substance abuse (e.g., drug use or excessive alcohol and nicotine use)
• Diagnosis of dissociative disorder (F44) in life history

Unmedicated, depressed patients (mildly or moderately depressed).

Depending on privacy regulation (removal of all connections to personal identifiers), the aim is to make the primary readout scores available.