evidence: The substantial increase in deaths by overdose and potential underlying suicidal intent in such deaths suggest the importance of understanding trends of suicidal ideation in individuals with opioid use disorder (OUD). This study aimed to examine the trends and correlates of past-year suicidal ideation (SI) and mental health service use among US adults with past-year OUD from 2009 to 2020. [...] Opioid and other drug-related overdoses and suicides are leading causes of injury death and represent a significant public health threat in the United States (U.S.). This study examined clinical factors of three patient groups from two inpatient addiction treatment facilities in Appalachian West Virginia (n = 66). Patients were classified as having: 1) unintentional overdose(s) (OD), 2) suicidal ideation or suicide attempt(s) (SI/SA), and 3) suicidal ideation or suicide attempt, and unintentional overdose (SI/SA/OD). Multinomial logistic regression models were used to determine whether adverse childhood experiences, self-injurious behaviors, substance use history, overdose history, and past year stressful life events were differentially associated with history of SI/SA/OD. Participants in the OD group were more likely to have used heroin in the 24-h preceding their most recent overdose compared to either the SI/SA or SI/SA/OD groups. The multivariable model found participants with history of SI/SA had higher adverse childhood experience scores and more participants with history of SI/SA endorsed childhood physical abuse and teen dating violence. Overall, there are characteristics that distinguish unintentional overdose from suicidal ideation and attempt. Patients with SI/SA/OD appear to have greater clinical severity.