The information requested is not held centrally and could be provided only at disproportionate cost.
In 1997, the Office for National Statistics undertook a survey of mental ill health in the prison population of England and Wales. This found that a higher proportion of prisoners had lower intellectual functioning scores than would be expected in the general population.
Further information is available in the report of this survey: “Psychiatric Morbidity Amongst Prisoners in England and Wales” (1998), a copy of which is available in the Library.