Personality traits among major depressive disorder in southern Thailand: a hospital-based case–control study

BACKGROUND: Residual depression can cause functional impairment. This study aimed to assess personality traits among individuals with depression, to compare the results with personality traits found in outpatients without psychiatric disorders recruited from general practitioner settings, and to study the association between personality traits and the age-onset of depression, duration of treatment, and the presence of depressive residual symptoms. METHODS: A case–control study surveyed Thai individuals with depression and outpatients without psychiatric disorders recruited from general practitioner settings at an outpatient clinic of Songklanagarind hospital, in 2022. The questionnaires were: (1) demographic data, (2) the PHQ-9 Thai version, and (3) the International Personality Item Pool-NEO (IPIP-NEO) Thai version. The difference between personality traits and the assigned clinical group were analyzed using the Student’s t-test and the Wilcoxon rank sum test. A generalized linear model was performed to examine differences of personality traits between the assigned clinical group (case–control), and the presence of depressive residual symptoms. The association between personality traits and treatment profiles was assessed by using an analysis of the variance test and the Kruskal–Wallis test. RESULTS: In regards to 73 individuals with depression in the case group, and 73 gender-and age-matched outpatients without psychiatric disorders recruited from general practitioner settings in the control group; 78.1% of cases and 82.2% of controls were female. Thirty-eight (52.1%) cases had depressive residual symptoms. Regarding the IPIP-NEO Thai version, there was a statistically significant difference in Neuroticism, Extraversion, and Conscientiousness domains between the case and the control groups. In comparison to the control group, the case group scored higher on the Neuroticism domain, and lower on the Extraversion and Conscientiousness domains. Every 0.18-point reduction in the Neuroticism score and every 0.09-point increment in regards to the Openness score were associated with a 1-year increment of age-onset of depression. This study found an association between a higher score of Neuroticism and a lower score of Conscientiousness with the presence of depressive residual symptoms. CONCLUSION: Different personality profiles were found between individuals with depression and outpatients without psychiatric disorders recruited from general practitioner settings. Individuals with depressive residual symptoms featured a higher score of Neuroticism and a lower score of Conscientiousness. A higher score of Neuroticism and a lower score of Openness were associated with age-onset of depression, but no personality traits were associated with treatment duration.