Reaction-time changes around rule shifts on the Wisconsin card sorting test in obsessive–compulsive disorder and treatment-resistant depression

Conventional Wisconsin Card Sorting Test (WCST) indices quantify errors and categorization performance, whereas reaction-time measures may provide complementary information about performance surrounding rule shifts. This study compared conventional WCST performance and rule-shift-related reaction-time patterns among patients with obsessive–compulsive disorder (OCD), patients with treatment-resistant depression (TRD), and healthy controls (HCs). This retrospective study included 181 participants: 38 with OCD, 67 with TRD, and 76 HCs. Reaction times before and after each of five WCST rule shifts were analyzed using generalized estimating equations (GEE), adjusting for age, sex, and education. Four conventional WCST indices were compared using Kruskal–Wallis tests, with Holm correction across the four omnibus tests. An additional exploratory analysis examined 19 conventional WCST indices, with Holm correction across these 19 tests. In the full GEE model, planned contrasts averaged equally across the five rule shifts showed a greater pre-to-post change in log-transformed reaction time in OCD than in HCs (β = 0.146, 95% CI 0.064–0.228; Holm-adjusted p = 0.00149) and in TRD than in HCs (β = 0.107, 95% CI 0.037–0.177; Holm-adjusted p = 0.00538). The OCD–TRD contrast was not statistically significant (β = 0.039, 95% CI − 0.046 to 0.123; Holm-adjusted p = 0.370). The group-by-phase-by-shift interaction was not statistically significant. None of the four primary conventional WCST omnibus tests or the 19 exploratory omnibus tests remained statistically significant after their respective Holm corrections. Both clinical-group differences remained significant in full-model sensitivity analyses addressing extreme reaction times, although the OCD–HC estimate was attenuated when very long reaction times were excluded; a contribution of medication to the TRD findings could not be excluded. Patients with OCD and TRD showed greater pre-to-post rule-shift reaction-time changes than HCs when estimates were averaged across five rule shifts. Robust group differences in conventional WCST indices were not established after correction for multiple testing. Reaction-time measures may complement conventional WCST indices, but independent replication is needed before clinical or mechanistic conclusions can be drawn.