Probing implicit learning in obsessive-compulsive disorder: Moderating role of medication on the weather prediction task

•The Weather Prediction Task (WPT) is a putative measure of implicit learning.•Patients with OCD and healthy controls completed the WPT.•Unmedicated patient with OCD showed subtle deficits in WPT performance.•Performance deficits were not evident for medicated patients with OCD.•Use of explicit learning strategies may mask deficits in implicit learning in OCD.

Deficits in implicit learning, a process by which knowledge is acquired accretively through practice independent of conscious awareness, have been implicated in Obsessive-compulsive disorder (OCD). The weather-prediction task (WPT) was used to assess implicit learning in 26 unmedicated patients with OCD and 23 healthy controls. An additional analysis compared these two groups with 25 medicated patients with OCD. In the comparison of unmedicated patients with healthy controls there was a subtle but statistically significant group-by-block interaction. Patients with OCD showed slower improvement in performance during the middle phase of learning. In a three-group comparison, there was no main effect of group; in post-hoc tests, medicated patients with OCD differed from unmedicated patients and were not different from healthy controls. Unmedicated patients with OCD have a subtle deficit in implicit learning in the WPT. This may be mitigated by pharmacotherapy, although prospective studies would be required to confirm this conclusion.