Psychosis, psychopathy, and homicide: a preliminary neuropsychological inquiry

This study attempted to statistically distinguish subgroups of murderers with mental disorders from among 26 hospitalized men (mean age=34 years) who were committed to a maximum security forensic hospital.

Measures consisted of objective ratings of psychosis and psychopathy and neuropsychological tests of intelligence, memory and attention, executive functions, and academic abilities.

Cluster analysis produced two distinct subgroups: one defined by high incidence of psychosis and low level of psychopathy and one by low incidence of psychosis and high level of psychopathy, each corresponding to distinct neuropsychological differences in intellectual abilities, learning disabilities, and social intelligence.

In light of this relatively small, highly select group, these novel findings must be viewed as preliminary. Studies of larger cohorts are needed before definitive conclusions can be drawn as to the reliability of these two distinct symptom clusters, each independently validated by neuropsychological measures of intelligence, sociality, and academic abilities.