Neurocognitive functioning in adults with trichotillomania: Predictors of treatment response and symptom severity in a randomized control trial.

Trichotillomania (TTM) is associated with impairments in response inhibition and cognitive flexibility, but it is unclear how such impairments relate to treatment outcome. The present study examined pre-treatment response inhibition and cognitive flexibility as predictors of treatment outcome, change in these domains from pre-to post-treatment, and associations with TTM severity. Participants were drawn from a randomized controlled trial comparing acceptance-enhanced behavior therapy (AEBT) to psychoeducation and supportive therapy (PST) for TTM. Adults completed assessments at pre-treatment (n = 88) and following 12 weeks of treatment (n = 68). Response inhibition and cognitive flexibility were assessed using the Stop Signal Task and Object Alternation Task, respectively. Participants completed the MGH-Hairpulling Scale. Independent evaluators administered the NIMH-Trichotillomania Severity Scale and Clinical Global Impressions-Improvement Scale. Higher pre-treatment TTM severity was associated with poorer pre-treatment cognitive flexibility, but not response inhibition. Better pre-treatment response inhibition performance predicted positive treatment response and lower post-treatment TTM symptom severity, irrespective of treatment assignment. Cognitive flexibility did not predict treatment response. After controlling for age, neither neurocognitive variable changed during treatment. Response inhibition and cognitive flexibility appear uniquely related to hair pulling severity and treatment response in adults with TTM. Implications for treatment delivery and development are discussed.