Eating disorder-related content in Reddit suicidal ideation posts: an LLM-assisted analysis of mental health comorbidities, substance use, and demographic patterns

Eating disorders are severe psychiatric conditions characterized by a markedly elevated risk of suicidal ideation and behavior. Although prior research has documented these associations in clinical settings, the underlying psychosocial and behavioral dynamics of such co-occurrence remain underexplored in non-clinical contexts, such as social media health narratives. This cross-sectional study examines the prevalence, demographic characteristics, and patterns of co-occurring mental health conditions and substance use among individuals who self-identify as having eating disorders and express suicidal ideation on Reddit’s r/SuicideWatch community. Using a validated keyword-based filtering framework informed by large language model–generated keyword expansion, we identified 688 eating disorder–related posts from a corpus of 27,434 suicidal ideation posts, representing a co-occurrence prevalence of 2.5% (95% CI: 2.33%–2.70%). Among posts with self-reported gender (n=75), females were the largest group (42.7%); among posts with self-reported age (n=170), individuals aged 18–20 were most represented (28.8%). Co-occurring mental health conditions were referenced in 79.0% of posts (95% CI: 75.8%–81.9%), particularly depression (43.9%) and anxiety (31.5%), alongside alcohol as the most prominent substance. These findings illustrate how social media discourse can complement clinical research in characterizing high-risk populations, with potential implications for the design of targeted digital mental health interventions for adolescents and young adults at the intersection of eating disorders and suicide risk.