Overcrowding in prisons - an issue in most prisons in Canada and other parts of the world - negatively impacts the mental and physical health of prisoners, states an article in CMAJ (Canadian Medical Association Journal).

Bill C-10, Canada's omnibus federal crime bill that will most likely increase prison populations, will have negative health consequences. "Bill C-10 will likely have a dramatic impact on the size of prison populations and the stability of prison environments," write Adelina Iftene and Allan Manson, Faculty of Law, Queen's University, Kingston, Ont. "We can expect an aggravation of the current state of overcrowding, an increase in correctional costs, more young people in custody, and prisoners spending longer periods in prison and being more isolated."

People in prisons have a higher rate of illness and mental health issues than the general population. For example, an estimated 37% of prisoners have hypertension compared with 1% in the general population, heart disease (30% v. 10%) and much higher rates of HIV infection and hepatitis C. Infectious diseases can spread in overcrowded prisons.

As of 2010, there were 13 531 prisoners in 57 federal institutions serving sentences of 2 years or more. Provincial and territorial prisons house people with sentences of less than 2 years. Most prisoners in Canadian prisons will at some point be released into the community.

"By incarcerating more people, exposing them to an increased potential for violence, and keeping them in prison longer, the system will further foster an environment of mental, emotional and physical degradation," conclude the authors.