Premeditated Murderers Are Twice As Likely To Have History Of Mood Disorders Than Impulsive Murderers

Mind of a murderer
Researchers have uncovered psychological differences in the minds of impulsive killers and those who kill with a plan in place. Wiki-Commons

Researcher Robert Hanlon from Northwestern University Feinberg School of Medicine has just finished conducting a one-of-a-kind study to analyze the neurophysiological and intelligence differences between impulsive murderers and those who kill in accord with a premeditated strategic plan.  

"It's important to try to learn as much as we can about the thought patterns and the psychopathology, neuropathology and mental disorders that tend to characterize the types of people committing these crimes," Hanlon explained.

"Ultimately, we may be able to increase our rates of prevention and also assist the courts, particularly helping judges and juries be more informed about the minds and the mental abnormalities of the people who commit these violent crimes."

Hanlon, an associate professor of clinical psychiatry and clinical neurology at Northwestern Medicine, classified 77 murderers from prison populations in Illinois and Missouri as either affective/impulsive murderers or premeditated/predatory murderers.

Each inmate was evaluated by Hanlon through a series of intelligence and neuropsychological tests to examine cognitive abilities such as memory, attention, and executive functions. The results of his investigation showed that 66 percent of murders who had a plan to kill already in place had a history of mood or psychotic disorders, while only 34 percent of impulsive murderers reported a similar history.

On the other hand, 59 percent of impulsive murderers were also developmentally disabled and had cognitive and intellectual impairments. Both groups reported high levels of alcohol or drug use — 93 percent of impulsive murderers and 76 percent of premeditated murderers — over time or at the time of the murder.

"Impulsive murderers were much more mentally impaired, particularly cognitively impaired, in terms of both their intelligence and other cognitive functions," Hanlon added.

"The predatory and premeditated murderers did not typically show any major intellectual or cognitive impairments, but many more of them have psychiatric disorders."

 

Source: Brook M, Stratton J, Jensen M, Rubin L, Hanlon R. Neuropsychological and Intellectual Differences Between Types of Murderers: Affective/Impulsive Versus Predatory/ Instrumental (Premeditated) Homicide. Criminal Justice and Behavior. 2013.

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