Dissimulation in forensic psychiatric evaluations, a case-control study of the Millon Clinical Multiaxial Inventory-III.

The possible tendency of subjects to decrease, hide, or omit symptomatic aspects of their mental functioning is one of the main problems in forensic psychological and psychiatric evaluations. We aimed at verifying the possible existence of significant differences in the Millon Clinical Multiaxial Inventory-III (MCMI-III) scales scores between a sample of dissimulators (n = 40) and their non-dissimulator counterpart matched by age, sex, and diagnosis. Cases and comparisons were retrieved from the archive of a single university forensic psychiatric centre between 2013 and 2022. Results showed statistically significant higher scores in the sample of dissimulators in the Desirability, Histrionic, Narcissistic, and Compulsive MCMI-III scales than in the comparison sample. Point biserial correlation test disclosed a strong positive correlation between the Desirability, Histrionic, Narcissistic, and Compulsive scales of the MCMI-III and being in the dissimulator group of subjects while a negative correlation emerged for all the other scales except drug dependence.

Key points: The forensic setting can affect a subject's behaviour.Dissimulation is a mechanism of minimization or concealment of a psycho-pathological condition.The MCMI-III can be a useful tool for a forensic psychiatrist or forensic psychologist in assessing dissimulation.