Suicide and Depression

This chapter focuses on the close relationship between suicide and depression, integrating global epidemiology, risk factors, assessment, and prevention strategies. Suicide remains a leading cause of mortality, especially in young and older populations. Suicidal ideation refers to thoughts of death or self-harm that do not always progress to behavior, while suicide risk denotes the probability of transition from ideation or other markers to attempt or completion. Suicidality spans this spectrum from ideation to fatal outcomes. Individuals with major depressive disorder and bipolar disorder show elevated risk, particularly during early diagnosis and in mixed or anxious episodes. Conceptual models recognize the non-linear, multifaceted nature of suicidality, supporting staging and narrative approaches that capture transitions from vulnerability to crisis. Such models emphasize that imminent risk may arise even without overt ideation, underscoring the need for repeated assessment. Risk prediction combines clinical evaluation, sociodemographic information, and emerging biomarkers, yet individual-level prediction remains difficult. Polygenic scores, inflammatory markers, and aging indices show potential, while machine learning with health records and voice analysis can improve short-term estimation when integrated with clinical expertise. Systematic assessment incorporates structured interviews and validated scales, including evaluation of personal, contextual, and protective factors. Prevention requires multilevel interventions involving policy, clinical treatment, environmental safety, and digital innovation. Pharmacological treatments, including antidepressants, lithium, and ketamine, with psychotherapies, remain essential. Safety planning, psychosocial support, and follow-up are vital in managing acute risk. Ultimately, effective suicide prevention demands coordinated efforts across healthcare, social services, and public health sectors, grounded in evidence and shared responsibility.