This peer support literature review analysed over 1000 research studies on peer support from around the world to find out who is involved in it, the type of support provided and why. The findings showed that peer support can take many forms, such as informal telephone calls, group get-togethers, online forums or structured training. Existing evidence examined by the review showed that peer support is worth investing in as a way of tackling long-term health conditions but knowledge on the service could be strengthened by commissioning more robust and detailed evaluations of the impacts and reasons why peer support works better in some contexts and for some groups.