Smaller amygdala volume and increased neuroticism predict anxiety symptoms in healthy subjects: A volumetric approach using manual tracing

Volume reductions in the amygdala (AMY) have been found in patients with anxiety disorders, but findings are mixed in subclinical participants with high trait anxiety scores, in whom both reductions and increases in AMY volume have been identified. One potential reason for such discrepancies could be the employment of different methods to determine the AMY volume (i.e., manual tracing in psychiatric research vs. automated methods), in non-patient research. In addition to trait anxiety, smaller AMY volume has also been linked to neuroticism, a personality trait consistently linked to increased vulnerability to anxiety. However, it is not clear how AMY volume and neuroticism together may contribute to anxiety symptoms in healthy functioning. These issues were investigated in a sample of 46 healthy participants who underwent anatomical MRI scanning and completed questionnaires measuring trait anxiety and neuroticism. AMY volume was assessed using manual tracing, based on anatomical landmarks identified in each participant's anatomical image. First, smaller left AMY volume was linked to higher levels of neuroticism (p = .013) and trait anxiety (p = .024), which in turn were positively correlated with each other. Moreover, AMY volume had a significant indirect effect on trait anxiety through neuroticism (ab = − .009, 95% CI [− .019, − .002]). This effect was not bidirectional, as trait anxiety did not predict AMY volume through neuroticism. Collectively, these findings provide support for a brain-personality-symptom framework of understanding affective dysregulation, which may help inform the development of prevention and intervention paradigms targeting preservation of AMY volume and reduction of neuroticism, to protect against anxiety symptoms.