Spider phobia is associated with decreased left amygdala volume: a cross-sectional study

Melanie S Fisler,Thomas Dierks,Leila M Soravia,Roland Wiest,Wolfgang Schmitt,Andrea Federspiel,Dominique J-F De Quervain,Helge Horn

doi:10.1186/1471-244x-13-70

Melanie S Fisler, Thomas Dierks + Show 6 more

Open Access

https://doi.org/10.1186/1471-244x-13-70

Copy DOI

Abstract

BackgroundEvidence from animal and human studies imply the amygdala as the most critical structure involved in processing of fear-relevant stimuli. In phobias, the amygdala seems to play a crucial role in the pathogenesis and maintenance of the disorder. However, the neuropathology of specific phobias remains poorly understood. In the present study, we investigated whether patients with spider phobia show altered amygdala volumes as compared to healthy control subjects.MethodsTwenty female patients with spider phobia and twenty age-matched healthy female controls underwent magnetic resonance imaging to investigate amygdala volumes. The amygdalae were segmented using an automatic, model-based segmentation tool (FSL FIRST). Differences in amygdala volume were investigated by multivariate analysis of covariance with group as between-subject factor and left and right amygdala as dependent factors. The relation between amygdala volume and clinical features such as symptom severity, disgust sensitivity, trait anxiety and duration of illness was investigated by Spearman correlation analysis.ResultsSpider phobic patients showed significantly smaller left amygdala volume than healthy controls. No significant difference in right amygdala volume was detected. Furthermore, the diminished amygdala size in patients was related to higher symptom severity, but not to higher disgust sensitivity or trait anxiety and was independent of age.ConclusionsIn summary, the results reveal a relation between higher symptom severity and smaller left amygdala volume in patients with spider phobia. This relation was independent of other potential confounders such as the disgust sensitivity or trait anxiety. The findings suggest that greater spider phobic fear is associated with smaller left amygdala. However, the smaller left amygdala volume may either stand for a higher vulnerability to develop a phobic disorder or emerge as a consequence of the disorder.

Highlights

Evidence from animal and human studies imply the amygdala as the most critical structure involved in processing of fear-relevant stimuli
Group analysis revealed that patients showed significant higher mean scores on the Spider Phobia Questionnaire (SPQ) (W=214.5, Z= -5.30, p=0.00)
Patients reported higher state anxiety (STAI-state) before scanning, but not after scanning (F [3,36]= 6.32; p= 0.25), suggesting patients suffering from anticipatory anxiety

Summary

Introduction

Evidence from animal and human studies imply the amygdala as the most critical structure involved in processing of fear-relevant stimuli. We investigated whether patients with spider phobia show altered amygdala volumes as compared to healthy control subjects. Converging evidence implies the amygdala as the most critical structure involved in processing of phobia-relevant, and general threatening stimuli [2,3,4,5,6]. In order to clarify the contribution of possible confounding factors, several aspects of phobic disorders that could be critical to the pathogenesis have to be considered. To the best of our knowledge, this is the first study investigating volumetric differences of the amygdala in SP compared to healthy control subjects

Objectives

Methods

Results

Discussion

Conclusion