Trichotillomania is a psychiatric condition characterized by repetitive pulling out of one's hair, leading to marked functional impairment. The aim of this study was to examine the association between duration of trichotillomania (defined as time between initial age of onset and current age) and structural brain abnormalities by pooling all available global data. Authors of published neuroimaging studies of trichotillomania were contacted and invited to contribute de-identified MRI scans for a pooled analysis. Freesurfer pipelines were used to examine whether cortical thickness and sub-cortical volumes were associated with duration of illness in adults with trichotillomania. The sample comprised 50 adults with trichotillomania (100% not taking psychotropic medication; mean [SD] age 34.3 [12.3] years; 92% female). Longer duration of illness was associated with lower cortical thickness in bilateral superior frontal cortex and left rostral middle frontal cortex. Volumes of the a priori sub-cortical structures of interest were not significantly correlated with duration of illness (all p > 0.05 uncorrected). This study is the first to suggest that trichotillomania is associated with biological changes over time. If this finding is supported by prospective studies, it could have important implications for treatment (i.e. treatment might need to be tailored for stage of illness). Viewed alongside prior work, the data suggest that brain changes in trichotillomania may be differentially associated with vulnerability (excess thickness in right inferior frontal cortex) and with chronicity (reduced thickness in medial and superior frontal cortex). Longitudinal research is now indicated.