Early intervention for adolescents at-risk for bipolar disorder: A pilot randomized trial of Interpersonal and Social Rhythm Therapy (IPSRT).

•Interpersonal and Social Rhythm Therapy (IPSRT) is feasible and acceptable to deliver to youth at high risk for bipolar disorder by virtue of a first-degree family history of the illness.•Few youth referred for community mental health services at intake initiated services over 6 month follow-up, highlighting the need for engagement efforts with this population.•No youth developed new-onset mood disorder over follow-up. Self- and parent-reported mood and non-mood psychiatric symptoms did not distinguish youth receiving IPSRT + Data-Informed Referral (DIR) for any psychiatric disorders present at baseline versus DIR-alone.•Per clinician ratings, 1 youth receiving IPSRT + DIR displayed subthreshold hypo/manic symptoms, versus 2 receiving DIR-alone over 6-months, possibly signaling less subthreshold hypo/manic symptoms, and for fewer weeks.•Although no self-reported measure of sleep distinguished the groups, we found a small effect for youth in the IPSRT + DIR group to evidence more wake after sleep onset (WASO; an index of sleep continuity) via actigraphy over follow-up.