CYOA App Intervention for Social Media Use in Adolescents With Depression (CYOA)

Adolescents randomized to this arm will use the CYOA app for 2 weeks. The app is designed to detect individualized social media use patterns and offer personalized options to disrupt problematic "runaway train" social media use.

The CYOA app is a personalized social media self-regulation intervention for adolescents with depression. Adolescents identify social media situations that may be harmful to their well-being and select preferred options for responding when those situations arise. When the app detects a "runaway train" social media use pattern based on predefined thresholds, it offers personalized options such as pausing use, modifying sensory intensity, engaging in mindfulness, or editing the feed to remove problematic content.

• CYOA App

Adolescents randomized to this arm will use social media as much or as little as preferred during the 2-week study period. They will still use the study app for data collection and complete the same study assessments as the intervention group.

Feasibility will be assessed by the number and proportion of days, out of 14 days, that adolescents assigned to the CYOA app use the intervention. The feasibility target is use of the app on at least 8 of 14 days.

Acceptability will be assessed using adapted Treatment Acceptability/Adherence Scale ratings with adolescents assigned to CYOA. Total score ranges from 9 to 63; higher scores indicate greater treatment acceptability/adherence. Create a separate outcome for qualitative interviews only if they are intended to be reported as an outcome, with a defined reporting measure.

Social media use patterns will be assessed using data extracted by the study app, including engagement patterns and app-based social media use data, and by self-report using the Social Media Use Scale. Social media use will be assessed using the Social Media Use Scale (SMUS). Total scores range from 17 to 153; higher scores indicate worse outcomes." Move app-derived engagement patterns into separate outcome entries once their specific measures are defined.

Daily mood will be assessed using ecological momentary assessment prompts with items from the Positive and Negative Affect Schedule short form.

Sleep will be assessed using the Pittsburgh Sleep Quality Index at study visits and daily ecological momentary assessment of hours slept during the 2-week intervention period. Sleep quality will be assessed using the Pittsburgh Sleep Quality Index (PSQI). Total scores range from 0 to 21; higher scores indicate worse sleep quality." Separate daily EMA hours slept.

Physical activity will be assessed using the Moderate to Vigorous Physical Activity screening measure and daily ecological momentary assessment of minutes of physical activity. Physical activity will be assessed using the Moderate to Vigorous Physical Activity (MVPA) screening measure. Scores range from 0 to 7; higher scores indicate better outcomes.

The number of meaningful in-person social interactions will be assessed using daily ecological momentary assessment (EMA) questions during the intervention period.

The duration of meaningful in-person social interactions will be assessed using daily ecological momentary assessment (EMA) questions during the intervention period.

Anxiety symptoms will be assessed using the Generalized Anxiety Disorder-7 scale.Anxiety symptoms will be assessed using the Generalized Anxiety Disorder-7 (GAD-7). Total scores range from 0 to 21; higher scores indicate greater anxiety symptom severity.

Well-being will be assessed using the Flourishing Scale (FS). Total scores range from 8 to 56, with higher scores indicating greater well-being.

Well-being will be assessed using the Satisfaction with Life Scale (SWLS). Total scores range from 5 to 35, with higher scores indicating greater life satisfaction.

Social connectedness will be assessed using the Social Connectedness Scale-Revised. Social connectedness will be assessed using the Social Connectedness Scale-Revised (SCS-R). Scores range from 0 to 6; higher scores indicate greater social connectedness

Depression symptoms will be assessed using the Children's Depression Inventory-2 (CDI-2), Child-Report. Scores range from 0 to 56; higher scores indicate greater depressive symptom severity.

Depression symptoms will be assessed using the Children's Depression Inventory-2 (CDI-2), Parent-Report. Scores range from 0 to 51; higher scores indicate greater depressive symptom severity.

Social media self-control failure will be assessed using the Social Media Self Control Failure scale. The study will evaluate whether CYOA is associated with greater decreases in social media self-control failure compared with no intervention. Social media self-control failure will be assessed using the Social Media Self Control Failure (SMSCF) Scale. Scores range from 3 to 15; higher scores indicate worse self-control failure.