Importance: Neurodegenerative diseases can cause dysfunction of neural structures involved in judgment, executive function, emotional processing, sexual behavior, violence, and self-awareness. Such dysfunctions can lead to antisocial and criminal behavior that appears for the first time in the adult or middle-aged individual or even later in life.
Objective: To investigate the frequency and type of criminal behavior among patients with a diagnosed dementing disorder.
Design, setting, and participants: We conducted a retrospective medical record review of 2397 patients who were seen at the University of California, San Francisco, Memory and Aging Center between 1999 and 2012, including 545 patients with Alzheimer disease (AD), 171 patients with behavioral variant of frontotemporal dementia (bvFTD), 89 patients with semantic variant of primary progressive aphasia, and 30 patients with Huntington disease. Patient notes containing specific keywords denoting criminal behavior were reviewed. Data were stratified by criminal behavior type and diagnostic groups.
Main outcomes and measures: Frequencies of criminal behavior and χ² statistics were calculated.
Results: Of the 2397 patients studied, 204 (8.5%) had a history of criminal behavior that emerged during their illness. Of the major diagnostic groups, 42 of 545 patients (7.7%) with AD, 64 of 171 patients (37.4%) with bvFTD, 24 of 89 patients (27.0%) with semantic variant of primary progressive aphasia, and 6 of 30 patients (20%) with Huntington disease exhibited criminal behavior. A total of 14% of patients with bvFTD were statistically significantly more likely to present with criminal behavior compared with 2% of patients with AD (P < .001) and 6.4% were statistically significantly more likely to exhibit violence compared with 2% of patients with AD (P = .003). Common manifestations of criminal behavior in the bvFTD group included theft, traffic violations, sexual advances, trespassing, and public urination in contrast with those in the AD group, who commonly committed traffic violations, often related to cognitive impairment.
Conclusions and relevance: Criminal behavior is more common in patients with bvFTD and semantic variant of primary progressive aphasia than in those with AD and is more likely to be an early manifestation of the disorder. Judicial evaluations of criminality in the demented individual might require different criteria than the classic "insanity defense" used in the American legal system; these individuals should be treated differently by the law. The appearance of new-onset criminal behavior in an adult should elicit a search for frontal and anterior temporal brain disease and for dementing disorders.