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.

Although thinking of suicide for some period of time (suicide ideation) is traditionally viewed as necessary to attempt suicide in the future, many people who engage in suicide behaviour do not report specific suicidal thoughts during clinical interviews. We wanted to know how to predict suicide in these subjects; therefore, we investigated a number of promising characteristics in two different age groups of depressed patients (sample 1: n = 230; age: 18–65 years; sample 2: n = 258; age >60 years) who were negatively tested for the presence of suicide ideation. As expected, SB was not rare in these groups. Among younger patients, suicide attempts were a little more frequent than in the other group (15 vs. 9%); they more often involved men, those who had been victims of sexual abuse in childhood, those who had negative thoughts about themselves or were predisposed to bipolar disorder. On the other hand, in old age, suicide risk was correlated with neurological problems, foremost alterations in language and movement disorders, and cholesterol levels. Thanks to this information, to determine suicide risk is still possible even when intent to die is not reported.