Can measures of cognitive flexibility and inhibition distinguish forensic psychiatric inpatients from prisoners?

We investigated whether forensic psychiatric inpatients can be distinguished from prisoners and healthy controls on the basis of their performance on cognitive tasks measuring cognitive flexibility (with a reversal learning task) and inhibition (with a stop signal task). Forensic psychiatric inpatients were expected to perform worse compared to prisoners. This study was based on pre-existing data from N = 241 males (119 forensic psychiatric inpatients, 57 prisoners and 65 healthy controls). We fitted logistic generalized linear models to group membership data using outcome measures from a stop signal task and a reversal learning task to examine whether deficiencies in inhibition and cognitive flexibility predict membership of the group of forensic psychiatric inpatients. Neurocognitive measures of cognitive flexibility, but not inhibition, had predictive value for group membership. This suggests that the capacity for cognitive flexibility may help differentiate between forensic subpopulations and healthy controls. Furthermore, our results highlighted substantial heterogeneity in cognitive performance in inhibition and cognitive flexibility within different offender groups. This study indicates that forensic subpopulations can be adequately differentiated based on neurocognitive measures of cognitive flexibility. In a broad sense, this study is an example of how neurocognitive approaches can contribute to refining diagnosis in forensic psychiatry.