Criminal Behaviour After Diagnosis of a Neurocognitive Disorder: A Nationwide Finnish Register Study.

OBJECTIVE: To explore criminal behavior of individuals with Alzheimer's disease (AD), frontotemporal dementia (FTD), or Lewy body dementias (LBD) after the diagnosis.

DESIGN: Nationwide register study.

SETTING: Information on diagnoses and criminality was received from Finnish registers. Crime types and incidences were compared between disorders and the general population.

PARTICIPANTS: All Finnish individuals diagnosed with AD, LBD, or FTD (n = 92 189) during 1998-2015.

MEASUREMENTS: Types of crimes and incidences, the standardized criminality ratio (SCR, number of actual crimes per number of expected crimes), numbers of observed cases, and person-years at risk counted in 5-year age groups and for both sexes and yearly.

RESULTS: Among men, at least one crime was committed by 2.8% of AD, 7.2% of FTD, and 4.8% of LBD patients. Among women, the corresponding figures were 0.4%, 2.0%, and 2.1%. The most frequent type of crime was traffic offence, followed by property crime. After age adjustment, the relative number of crimes between groups did not differ, except that men with FTD and LBD committed more crimes than those with AD. The SCR (95% CI) among men were 0.40 (0.38-0.42) in AD, 0.45 (0.33-0.60) in FTD, and 0.52 (0.48-0.56) in LBD. Among women, these were 0.34 (0.30-0.38), 0.68 (0.39-1.09), and 0.59 (0.51-0.68).

CONCLUSIONS: The diagnosis of a neurocognitive disorder does not increase criminal behavior, but rather reduces it by up to 50%. Differences in crime activity are present between different neurocognitive disorders and between the sexes.