Abstract
Objective: Personality traits serve as a transdiagnostic tool and may contribute to the clinical diversity of major depressive disorder (MDD) through shared neurobiological mechanisms. In the Pankseppian affective neuroscience perspective, SADNESS, FEAR, and ANGER as affective personality traits have been shown to play a role in the development of MDD. However, the relationship between depressive symptoms and affective personality traits is not well understood. The aim of this study is to investigate the longitudinal relationship between depressive symptoms and affective personality traits.
Methods: The study included 60 patients diagnosed with MDD and 53 healthy controls (HCs). The Structured Interview Guide for the Hamilton Depression Rating Scale Seasonal Affective Disorder version (SIGH-SAD), the Hamilton Anxiety Rating Scale (HAM-A), as well as the Affective Neuroscience Personality Scales (ANPS) and the Rumination Response Scale (RRS) were administered to all participants at baseline and follow-up, with an interval of 4–8 weeks. Group-time interactions for clinical variables and affective system scores were evaluated using linear mixed-effects analysis (LME). Following the findings obtained from the LME analyses, the mediating effects of brooding and psychic anxiety were examined in the relationship between changes in SADNESS and atypical symptoms and melancholic features. Statistical analyses were conducted using the R 4.1.1.
Results: Patients had higher negative affective system scores with medium to large effect sizes at baseline. In addition, while the PLAY score was higher in HC, there was no significant difference between the groups in terms of SEEKING and CARE scores. The relationships between affective systems and symptoms exhibited partially overlapping but different patterns in patients and HCs. During follow-up, SADNESS, FEAR, and ANGER scores decreased, while the PLAY score increased in patients; however, there were no changes in the affective system scores of the HCs. Change in SADNESS was positively correlated with changes in the HDRS-17 total score, melancholic features, atypical symptoms, the psychic anxiety subscale of the HAM-A, and brooding-type rumination. A significant relationship was also observed between FEAR and atypical symptoms. However, no significant associations were found between ANGER and any clinical variables. In addition, changes in the PLAY score were negatively correlated with both the somatic anxiety subscale and the total scores of the HAM-A. Mediation analyses revealed that changes in SADNESS had a positive direct effect on brooding and psychic anxiety. Additionally, psychic anxiety fully mediated the effect of SADNESS on melancholic features and atypical symptoms.
Conclusion: These findings suggest that affective personality traits, particularly SADNESS, play a dynamic role in the clinical presentation and progression of MDD. The identified mediating roles of brooding and psychic anxiety highlight potential transdiagnostic mechanisms linking primary affective systems to specific symptom profiles. Understanding these pathways may contribute to more individualized and biologically informed approaches to the assessment and treatment of depression. The findings of our study may be instructive for future neuroimaging studies.

Key words: Affective Personality Traits, Atypical Symptoms, Follow-up, Major Depressive Disorder, Melancholic Features, Rumination