The Prison Service holds in its care some of the most vulnerable, mentally ill people in England and Wales. The Department of Health has estimated that up to 5,000 of the people being held at any one time have such poor mental health they should not be held in an ordinary prison setting. 

In a parliamentary answer on 13 February 2006, ministers told MPs that the most comprehensive national assessment to estimate the incidence of mental health needs in prison was published in the Office of National Statistics (ONS) survey of mental illness in the prison populations of England and Wales in 1997. This indicated 90% of prisoners suffer from at least one mental health disorder.  As the All Party Parliamentary Group on Prison Health noted in its 2006 report, many of these will suffer from ‘common’ problems like depression and anxiety. A smaller but significant number will have more ‘severe’ problems such as schizophrenia or have a personality disorder. 20% of all prisoners have four of the five major mental health disorders.

Imprisonment affects very many families.  According to the Department for Children, Schools and Families, 7% of children during their school years will experience the imprisonment of a parent, usually their father. However, 18,000 children a year are separated from their mothers, usually for the first time, by her being taken into custody. When this happens most children are handed to relatives or friends and some go into care. Only 5% of the children of imprisoned mothers stay in the family home. In 2006, figures show that more children were affected by the imprisonment of a parent than by divorce in the family. On 15 February 2008 there were 81,918 people in prison in England and Wales.  Each year around 130,000 people enter the prison system including just under 12,000 women and nearly 5,300 children under the age of 18.