Suicide in prisons. Reflection of the communities served, or exacerbated risk?

Background: A recent review showed that opioid users' deaths from suicide were 10 times as common as expected on the basis of age and gender. Surveys showing prisoners' high prevalence of injecting or opioid dependence have led to a new statistical approach to prison suicides.
Aims: To estimate the expected number of UK prison suicides annually, having taken account of inmates' age, gender and opioid dependence.
Method: By gender, estimate the effective number of individuals (in terms of community-equivalent suicide risk) for whom prisons have a duty of care as 10 times the number of opioid-dependent inmates plus the number of non-opioid user inmates. Apply the gender and age-appropriate national suicide rates to work out the expected number of prison suicides.
Results: The Scottish Prison Service can expect 7.1 suicides per annum, and annual totals up to 12 without exacerbation of suicides due to incarceration. For the Prison Service in England and Wales, 19.3 suicides per annum can be expected in prisons, and annual totals may range up to 28 without indicating incarceration; the total of self-inflicted deaths was 47 in 1993-94.
Conclusions: Prisons cannot prevent all suicides. An alert may be warranted if prison suicides exceed 12 per annum in Scotland, or 28 in England and Wales.