Mentally ill people are overrepresented in United States jail and prison populations relative to the general population. There are three times more seriously mentally ill persons in jails and prisons than in hospitals in the United States. The exact cause of this overrepresentation is disputed by scholars; proposed causes include the deinstitutionalization of mentally ill individuals in the mid-twentieth century; inadequate community mental health treatment resources; and the criminalization of mental illness itself. The majority of prisons in the United States employ a psychiatrist and a psychologist. While much research claims mentally ill offenders have comparable rates of recidivism to non-mentally ill offenders, other research claims that mentally ill offenders have higher rates of recidivism. Mentally ill people experience solitary confinement at disproportionate rates and are more vulnerable to its adverse psychological effects. Twenty-five states have laws addressing the emergency detention of the mentally ill within jails, and the United States Supreme Court has upheld the right of inmates to mental health treatment.