The Penrose hypothesis in 2004: patient and prisoner numbers are positively correlated in low-and-middle income countries but are unrelated in high-income countries.

OBJECTIVE: To examine the relationship between the numbers of psychiatric hospital beds and prisoners using recent statistics.
DESIGN: An analysis of published data from 158 countries.
METHODS: Multiple linear regression techniques were used to examine the relationship between per capita measures of income and numbers of psychiatric hospital beds and the dependant variable of per capita prison populations, in high and low-and-middle-income countries.
RESULTS: Prison and psychiatric populations were positively correlated in low-and-middle-income countries. There was no relationship between the number of psychiatric hospital beds and prison populations in high-income countries.
CONCLUSIONS: In low-and-middle income countries the association between prison and psychiatric hospital populations may depend on the ability of governments to pay for custodial institutions as well as differences in cultural attitudes towards abnormal and criminal behaviour. In high-income (HI) countries psychiatric and prison populations are not related and probably determined by separate social and political factors.