PROJECT SUMMARY/ABSTRACT Suicide is now the 2nd leading cause of death among children ages 10-14 (CDC, 2022). This proposal responds to this public health crisis by testing an intergenerational mechanistic model of suicide risk in children while simultaneously testing a prevention and intervention approach that could be immediately useful. We focus on children whose mothers have a history of suicidal behavior (intent, planning, attempt) as an especially vulnerable group with increased risk for an early and persistent course of suicidal thoughts and behaviors (STB). Theory and research point to emotion regulation (ER) as a potential intergenerational mechanism of suicide risk transmission from mother to child. Maternal ER affects child ER development via maternal emotion socialization, whereby maternal responses to child’s emotions (validating/supportive vs. invalidating/unsupportive) shape how the child identifies, expresses, and modulates their emotions. We theorize that maternal ER, a prerequisite for optimal maternal emotion socialization, serves as a clinically and etiologically significant pathway through which maternal history of suicidal behavior impacts the continued development of child ER and emerging STB and other mental health problems into adolescence. This proposal maximizes impact by leveraging a randomized controlled trial of Dialectical Behavior Therapy (DBT) Skills Training to improve maternal ER and testing a mechanistic model of suicide risk transmission from mothers to their children during a critical developmental juncture for the emergence and rapid accelaration of STB and other mental health problems. Mothers will be randomized (1:1) to 6 months of either DBT Skills Training or Treatment As Usual (TAU), with expectation that mothers with a history of suicidal behavior + ER difficulties who are randomly assigned to DBT Skills Training will experience improvements in ER relative to mothers assigned to TAU. We hypothesize that DBT skills-driven improvements in maternal ER will predict meaningful decreases in child STB from late childhood into early adolescence through improved maternal emotion socialization and subsequent improvements in child ER. We will enroll 250 mother-child dyads with children ages 9-11 across mother-child dyads. Dyads will complete repeated multimodal assessments of maternal and ER, maternal emotion socialization, and child STB and other mental health problems over 24 months: baseline (intervention initiation), 3 months (intervention mid-point) 6 months (intervention termination), 12- and 24-months (post-intervention follow-up) when children will be ages 11-13, a high-risk time for STB emergence and the onset of other mental health problems. Additionally, in families with two caregivers, fathers/other caregivers will be invited to complete an assessment battery measuring history of suicidal behavior and psychopathology, ER, and emotion socialization to support an exploratory examination of these influen...