Title: Is anhedonia a mediating factor between depression and suicidal and self-injury ideation? A longitudinal analysis Authors: Amber T. Pham, Jennifer C. Veilleux, Melissa J. Zielinski, Michael R. Nadorff, & E. Samuel Winer Abstract (50/50 words): We examined if anhedonia mediated the relationship between depression and suicidal and self-injury ideation. Analyses show that through recent changes in anhedonia, depression predicts suicidal and self-injury ideation, but does not predict self-injury behavior. These results suggest anhedonia appears as the primary depressive symptom responsible for suicidal and self-injury ideation. Summary (434/500 words): Suicide attempts and suicidal ideation are symptoms often associated with depression. Depression has many other symptoms, one of which is anhedonia. Anhedonia is the loss of pleasure in something that was once found enjoyable, such as a hobby. Changes in anhedonia include the amount of pleasure lost or gained over time. We predicted that anhedonia is a mediating factor linking depression and suicide. Therefore, we examined if changes in anhedonia predicted suicidal ideation, non-suicidal self-injury ideation, and/or self-injury behavior when depression was controlled for. Participants in this study were people who were invited from a larger sample of Amazon Mechanical Turk “workers.” These Amazon Mechanical Turk workers are paid small amounts of money to do online tasks, such as completing surveys. Invited participants indicated a history of suicide attempt or self-injury on an initial survey, which included measures of risk behaviors, symptoms of depression and recent changes in anhedonia. The current sample (*N *= 93; M*age* = 32.26; 61.3% female) was invited back to complete more extensive measures about emotion, symptoms of distress, suicidal ideation and non-suicidal self-injury through Amazon Mechanical Turk. Average time between waves was 29.42 days. In this analysis, depression and changes in anhedonia were measured at time 1 while outcome behaviors were measured at time 2. This study examined direct and indirect effects in mediated regression models using 95% bootstrapped confidence intervals of 1000 samples. Significance is indicated if zero is not included in the confidence intervals. Results indicated that when controlling for anhedonia, there was not a direct effect of depression on suicidal ideation. However, there was an indirect effect of depression on suicidal ideation via recent changes in anhedonia. Anhedonia also partially mediated the relationship between depressive symptoms and past-month self-injury ideation, with a remaining direct effect in addition to a significant indirect effect. Neither depression nor changes in anhedonia predicted engagement in self-injury within the past-month. With depression, people are often fatigued, have trouble sleeping and have feelings of hopelessness along with losing interest in things that they used to find pleasure in. These results are consistent with anhedonia being the symptom, above and beyond other symptoms of depression that predicts suicidal ideation. This study contributes useful information that is applicable to prevention and treatment of self-injury ideation and behavior. Although our results with depression and anhedonia did not predict actual suicide attempts, these results could lead to future studies and information on how to predict and reduce suicide and self-injury ideation by reducing or treating anhedonia. Future studies could examine depressed people with anhedonia using psychotherapy and medication to specifically target anhedonia, or potentially screening for changes in anhedonia in individuals with sub threshold depressive symptoms.