Behavioral mediators of stress-related mood symptoms in adolescence & young adulthood

•Social withdrawal mediates the relationship between daily stress and anhedonia.•Impulsivity mediates the relationship between daily stress and manic symptoms.•Data-driven clustering reveals subgroups with distinct profiles of stress reactivity.•Stress-reactivity subgroups extend and complement diagnostic categories.•Clustering reveals prevalence of mixed symptom courses within unipolar diagnoses.