Suicide is the 2nd leading cause of death among adolescents in the U.S., and, alarmingly, suicide rates have increased significantly in this age group over the past decade. Effective suicide prevention for youth requires a comprehensive approach incorporating a range of upstream and downstream strategies. Crisis hotlines are one of the oldest downstream approaches in the U.S. "viewed as a national "safety net," providing essential support and resources during a suicidal crisis. Nearly two decades of research have supported the effectiveness of adult-run crisis hotlines for adults. Teen-to-teen (t2t) crisis lines are a specific type of crisis service in which youth volunteers help their similarly aged peers (through texts, chats, calls, and emails). Although t2t lines have the potential to offer a unique experience both for the youth who utilize the lines and the youth volunteers who staff them, there have been longstanding concerns about, and limited evidence to support, the safety and impact of these t2t lines for youth. To first address this crucial gap, this project will examine the impact, and critically the safety, of t2t crisis lines for youth volunteers. Notably, before we examine the effectiveness of t2t lines, we need to know if it is safe for youth to do this work. Youth volunteers may benefit from the t2t experience (e.g., helping peers), but there also is potential for this experience to be negative or harmful (e.g., increasing suicide risk). Research to date (all with adults) examining the impact of crisis line work on staff/volunteers has been mixed" some studies have observed a positive impact and others a negative one. It is essential to examine the impact on youth volunteers specifically, as young people may be particularly vulnerable to the stress of crisis line work. The proposed project will be the first to examine the impact of t2t crisis line work for youth volunteers (14-20 years-old) in collaboration with two of the largest t2t lines in the U.S." Teen Line (Los Angeles, CA, receives over 21,000 contacts/year) and Youth Line (Portland, OR, receives over 28,000 contacts/year). The aims of the project are: (1) to examine the negative impact, and specifically the safety, of t2t line volunteerism on youth volunteers, (2) to examine the positive impact of t2t crisis line volunteerism on youth volunteers, and (3) to examine volunteer (e.g., lived experience with mental health conditions) and crisis line factors (e.g., supervisor support) that may impact volunteers' experience on the t2t crisis line. This research is in line with several national funding priorities, including AFSP's new priority area to evaluate technological tools for suicide prevention, the National Action Alliance for Suicide Prevention's priority to examine "What services are most effective for treating the suicidal person and preventing suicidal behavior?", and the National Institute of Mental Health's special interest in suicide prevention crisis services. If t2t volunteerism is found to be safe and beneficial for youth, the next step in this research will be to examine the effectiveness of t2t crisis lines for youth who utilize these services.