The Liman Center at Yale Law School. (2020). Time-in-Cell 2019: A Snapshot of Restrictive Housing. Note: The Liman study reports up to 62,000 people in solitary confinement, but does not include the Federal Bureau of Prisons, local correctional facilities or juvenile facilities. Including those populations changes the estimate to between 80,000 and 100,000 in solitary confinement.
 Grassian, Stuart “Psychiatric Effects of Solitary Confinement” Washington University Journal of Law & Policy vol. 22 (2006)
Williams, B.A., Li, A., Ahalt, C. et al. The Cardiovascular Health Burdens of Solitary Confinement. J GEN INTERN MED 34, 1977–1980 (2019).