Social anxiety disorder (SAD) is one of the most common mental health disorders in youth, defined by a persistent and intense fear of negative evaluation by others. Recent research has examined its neurological underpinnings, including structural connectivity changes in the brain. This has been examined through measurement of the white matter (WM) structure of fibre pathways. Previous studies have shown inconsistent results. This study attempts to resolve these inconsistencies by utilising a recently proposed, advanced method for diffusion MRI analysis, known as fixel based analysis (FBA). This technique enables examination of WM macro- and micro-structure with measures of fibre density (FD), fibre bundle cross-section (FC) and fibre density-cross-section (FDC). This study evidenced increased FDC in a region of the right superior longitudinal fasciculus (SLF) from a whole brain FBA, along with increased FC and FDC from an analysis restricted to a-priori tracts of interest, in regions of the right inferior longitudinal fasciculus (R-ILF). The average FDC of the left uncinate fasciculus (L-UF) was also increased. To examine the relationship between WM structure and severity of symptoms, these FBA metrics were correlated with Leibowitz Social Anxiety Scale (LSAS) scores. From the tract-restricted analysis an inverse correlation between FC and LSAS scores was found in the R-ILF. The average FC of the R-ILF was also inversely correlated with symptom severity. By utilising a more sensitive and fibre-specific method of analysis than previous studies, these findings highlight innovative outcomes relating to white matter in numerous fibre tracts.

社交焦虑症 (SAD) 是青少年最常见的心理健康障碍之一，定义为对他人的负面评价持续而强烈的恐惧。最近的研究检查了其神经学基础，包括大脑中的结构连接变化。这已经通过测量纤维通路的白质 (WM) 结构进行了检查。先前的研究显示出不一致的结果。本研究试图通过利用最近提出的先进的扩散 MRI 分析方法（称为基于固定素的分析 (FBA)）来解决这些不一致问题。该技术可以通过测量纤维密度 (FD)、纤维束横截面 (FC) 和纤维密度横截面 (FDC) 来检查 WM 的宏观和微观结构。该研究证明，全脑 FBA 的右侧上纵束 (SLF) 区域的 FDC 增加，以及右侧下纵束区域的 FC 和 FDC 增加，这些分析仅限于先验感兴趣的区域。 R-ILF）。左钩状束 (L-UF) 的平均 FDC 也增加。为了检查 WM 结构与症状严重程度之间的关系，将这些 FBA 指标与 Leibowitz 社交焦虑量表 (LSAS) 分数相关联。从道受限分析中，在 R-ILF 中发现了 FC 和 LSAS 分数之间的负相关。R-ILF 的平均 FC 也与症状严重程度呈负相关。通过使用比以前的研究更敏感和纤维特异性的分析方法，