Cross-sectional and longitudinal relationships between complete blood count measures and adolescent suicidal behavior

•Complete blood count indices may be related to suicide attempt/ideation (SA/SI).•Adolescents with SA had lower eosinophil levels than those with SI.•Lower eosinophil levels in adolescents predicted suicidal behavior over 90 days.•Eosinophil levels may be a risk marker for future suicidal behavior.