Criminologist Prof David Wilson of Birmingham City University, who once worked on the sex offender treatment programme at Grendon prison, says psychological profiling can indicate whether such a criminal is less likely to re-offend - but ultimately, the nature of the offence makes it impossible to be absolutely certain.

BBC: Who, what, why: When is a sex offender not a risk?

There has been huge investment in better treatment for depression in the UK in recent years with the Improving Access to Psychological Therapies programme in England set up to widen access.

BBC: Depressed woman