Provision of support for MH in prision is challenging, often there are complex needs and circumstances. The difficulty with these figures, not just within prisons but within the general population, is conflating SH with attempted suicide. From the SPS data, though this is conceded, the distinction is not clear. It would be interesting to se what had changed in terms of reporting or indeed if ScotGov HEAT targets on suicide for training are being to bite? What is different now and why they apparent increase in so short a time?
Generally speaking (and I mean generally) deliberate SH is a coping strategy in reaction to complex emotional antecendents. Deliberate SH can often migate suicidial ideation. And with support main who SH can go on to managed this and be well.
UK stats on suicide are complicated with SH being included in attempted suicide figures where a person presents at A&E with injuries. This makes it very difficult to get clear picture of SH rates and those of attempted suicide. They are very different behaviours. Crudely put: SH is generally about emotional regulation and maintaining life, attempts at suicide is on the whole, the opposite of this.
The SAMS report on suicide is comprehensive and you can find that here http://www.samaritans.org/about-us/our-research/facts-and-figures-about-suicide
Also Dr Susan Rasmussen at Strathclyde, amongst others, has done a lot of reseach on SH and Suicide for anyone interested.
Finally ScotGov response to MH... well that's something for another day. However there has been some spend directed towards MH (see Mental Health Strategy 2012 - 2015 and recent updated). There is no additional provision for prisons as I understand it, but happy to be corrected on that (not from the POV SH and Suicide etc, perhaps from Violence/Aggression etc).
If I have misrespresented anyone or anything in this post, I'm happy to explore that