The effects of the dark tetrad personality traits on aggression levels, self-injury behaviors and suicide probability in patients with major depressive disorder

This study aims to examine the effects of Dark Tetrad personality traits (machiavellianism, narcissism, psychopathy, and sadism) on aggression levels, non-suicidal self-injury (NSS) and suicide probability in individuals diagnosed with major depressive disorder (MDD). This cross-sectional study was conducted between February 2023 and November 2024, with the target population consisting of individuals residing in Istanbul. The sample of the study consists of a total of 140 participants who met the specified inclusion and exclusion criteria. In this context, the sample group consisted of two subgroups. The clinical group consisted of 70 individuals diagnosed with MDD who were receiving treatment in the psychiatry outpatient clinic and psychiatry ward of Erenköy Mental and Neurological Diseases Training and Research Hospital. The control group consisted of 70 individuals without any psychiatric diagnosis, selected voluntarily and through convenience sampling. Data were collected using the Personal Information Form (PIF), the Structured Clinical Interview for DSM-5 Disorders – Clinician Version (SCID-5-CV), the Beck Depression Inventory (BDI), the Short Dark Tetrad (SD4), the Buss-Perry Aggression Questionnaire (BPAQ), the Suicide Probability Scale (SPS), and the Inventory of Statements about Self Injury (ISAS), all of which were administered in their Turkish-adapted versions. Frequency distribution, independent samples t test, Mann-Whitney U test, Pearson correlation, Spearman correlation, Chi-square test and simple linear regression analyses were used in the analysis of data. The findings showed that the dark tetrad personality traits, aggression, NSS and suicide probability scores of the clinical group were statistically significantly higher compared to the control group. Correlation analyses revealed that there were positive and strong relationships, particularly between depression levels and aggression and suicide probality. Dark Tetrad personality traits were only associated with aggression among the main variables in the clinical group, but were associated with all main variables in the control group and the entire sample. Regression analyses revealed that Dark Tetrad personality traits have a significant predictive effect on aggression, but they no not show a significant predictive effeck on suicide probality or NSS. The findings suggest that dark personality traits are primarily associated with externalizing behavioral risks in individuals with major depression. In this context, it is thought that it is important to consider not only mood symptoms but also personality organization in the clinical evaluations of individuals diagnosed with major depression. It is anticipated that the obtained data will contribute to risk assessment and intervention processes in both clinical psychology and forensic psychology.