Major Mental Illness as a Risk Factor for Incarceration

Individuals with serious mental illness are overrepresented in correctional populations. However, little is known about the representation of persons with serious mental illness at earlier stages in the criminal justice process. This research sought to measure the prevalence of arrestees in New York State who were treated for a major mental illness in the year before their arrest and to assess whether these individuals had a disproportionate rate of incarceration.

Approximately 600,000 individuals arrested in New York State between January 1, 2010, and December 31, 2013, were matched against public mental health records to identify defendants diagnosed as having a major mental illness in the 12 months before their arrest.

Between 4% and 6% of the arrestees were diagnosed as having a major mental illness during a mental health service visit in the 12 months prior to their arrest. A major mental illness diagnosis was associated with more than a 50% increase in the odds of a jail sentence for misdemeanor arrestees, after the analyses controlled for the other case characteristics. Conversely, it was unrelated to the likelihood of a prison sentence given a felony arrest, but it did moderate the effect of other case characteristics within the group of arrestees with felonies.

Differential adjudication of misdemeanor arrestees with a major mental illness diagnosis appears to contribute to their overrepresentation within the jail population. The role that poverty and pretrial incarceration may play in this relationship was not explored in this research and should be the subject of future investigation.