Alexithymia mediates white-matter microstructure and substance use escalation in trauma-exposed individuals

Alexithymia has been separately associated with differences in white-matter and with substance use (SU). Childhood trauma has also been associated with white-matter differences, alexithymia, and SU. This study explored the moderating effect of childhood trauma on the indirect effect of white-matter microstructure on SU escalation through alexithymia.

Participants were 44 young adults from a larger longitudinal cohort, and data on childhood trauma, alexithymia, white-matter were acquired initially. SU escalation was calculated from the quantity and frequency of SU initially and two-years later. Diffusion-weighted white-matter data were used to calculate tensor-derived and crossing-fiber anisotropy measures. Multivariable analyses and moderated mediation models tested whether the indirect relationship between corpus callosum anisotropy and SU escalation through alexithymia differed between levels of childhood trauma.

Splenium primary-fiber anisotropy correlated with lower SU escalation whereas splenium secondary-fiber anisotropy correlated with greater SU escalation and alexithymic difficulty describing feelings. Within moderated mediation models, childhood trauma levels moderated associations between splenium primary-fiber anisotropy and difficulty describing feelings. Conditional effects showed that at greater childhood trauma, lower splenium primary-fiber anisotropy associated with greater difficulty describing feeling, and difficulty describing feelings mediated associations between splenium primary-fiber anisotropy and SU escalation.

Trauma may moderate maladaptive emotion-language processing in individuals with specific white-matter differences, and alexithymia may be directly or indirectly associated with SU escalation. Individuals with early-life trauma and splenium white-matter differences may represent a vulnerable population, which may be an important focus from interventions that bolster stress management and emotion regulation.