Marcus, John, and Edens more recently performed a series of statistical analyses on PPI scores and concluded that psychopathy may best be conceptualized as having a "dimensional latent structure" like depression. repeated the study on a larger sample of prisoners, using the PCL-R and seeking to rule out other experimental or statistical issues that may have produced the previously different findings.
Detailed, comprehensive psychiatric, neurological, and neuropsychological evaluations have uncovered a multitude of signs, symptoms, and behaviors indicative of such disorders as bipolar mood disorder, schizophrenia spectrum disorders, complex partial seizures, dissociative identity disorder, parasomnia, and, of course, brain damage/dysfunction.
Otto Kernberg, from a particular psychoanalytic perspective, believed psychopathy should be considered as part of a spectrum of pathological narcissism, that would range from narcissistic personality on the low end, malignant narcissism in the middle, and psychopathy at the high end.
Psychopathy, narcissism and Machiavellianism, three personality traits that are together referred to as the dark triad, share certain characteristics, such as a callous-manipulative interpersonal style.
Psychopathy has also been linked to high psychoticism—a theorized dimension referring to tough, aggressive or hostile tendencies.
Aspects of this that appear associated with psychopathy are lack of socialization and responsibility, impulsivity, sensation-seeking (in some cases), and aggression.
They suggest that while for legal or other practical purposes an arbitrary cut-off point on trait scores might be used, there is actually no clear scientific evidence for an objective point of difference by which to label some people "psychopaths"; in other words, a "psychopath" may be more accurately described as someone who is "relatively psychopathic".