Neurological, Metabolic, and Psychopathological Correlates of Lifetime Suicidal Behaviour in Major Depressive Disorder without Current Suicide Ideation

Introduction: Suicidal behaviour (SB) has a complex aetiology. Although suicidal ideation (SI) is considered the most important risk factor for future attempts, many people who engage in SB do not report it. Methods: We investigated neurological, metabolic, and psychopathological correlates of lifetime SB in two independent groups of patients with major depression (sample 1: n = 230; age: 18–65 years; sample 2: n = 258; age >60 years) who did not report SI during an index episode. Results: Among adults (sample 1), SB was reported by 141 subjects (58.7%) and severe SB by 33 (15%). After controlling for interactions, four risk factors for SB emerged: male gender (OR 2.55; 95% CI: 1.06–6.12), negative self-perception (OR 1.76; 95% CI: 1.08–2.87), subthreshold hypomania (OR 4.50; 95% CI: 1.57–12.85), and sexual abuse (OR 3.09; 95% CI: 1.28–7.48). The presence of at least two of these factors had the best accuracy in predicting SB: sensitivity = 57.6% (39.2–74.5); specificity = 75.1% (68.5–82.0); PPV = 27.9% (20.9–37.2); NPV = 91.4% (87.6–94.1). In older patients (sample 2), 23 subjects (9%) reported previous suicide attempts, which were characterized by earlier onset (25 years: OR 0.95: 0.92–0.98), impaired verbal performance (verbal fluency: OR 0.95: 0.89–0.99), higher HDL cholesterol levels (OR 1.04: 1.00–1.07) and more dyskinesias (OR 2.86: 1.22–6.70). Conclusion: Our findings suggest that SB is common in major depressive disorder, even when SI is not reported. In these individuals it is feasible and recommended to investigate both psychiatric and organic risk factors. The predictive power of models excluding SI is comparable to that of models including SI.