If the systematic review and/or meta-analysis sits at the top of the evidence-based pyramid then a systematic review of existing systematic reviews in a particular area should perhaps be the cherry on the top.
The paper published by Katharine Smith & Andrea Cipriani  is that cherry on top of the pyramid, looking at a topic of some interest to some of this authorship group  on how the "evidence to date is overwhelmingly in favour of lithium as an antisuicidal agent."
I've talked about lithium a few times on this blog (see here and see here) including research pertinent to the idea that the lithium content of public drinking water supplies might show an interesting *relationship* with suicide rates roundabout (see here). Such work stemming from the idea that lithium might have some rather important (positive) influences on suicide prevention  for whatever reason(s).
Smith & Cipriani searched the peer-reviewed literature for "systematic reviews and meta-analyses of RCTs [randomised controlled trials] of lithium and suicide and self harm." They found a handful of papers meeting their guidance and with them 'overwhelming' evidence that lithium does seem to impact on risk of suicide. They comment on the fact that there is more to do in this area; for example on: "the supporting evidence that observational and non-randomized studies can also provide" but present an important case that lithium use "should be incorporated more assertively into current guidelines" when it comes to suicide prevention.
Bearing in mind the cost-benefit profile of lithium  and that suicide - whether ideation, attempt or completion - stems from a complicated (and often individual) set of circumstances, this is one area where the term 'life-saving' is not to be under-emphasised. And I can think of at least one label where quite a bit more 'life-saving' is required (see here)...
 Smith KA. & Cipriani A. Lithium and suicide in mood disorders: Updated meta-review of the scientific literature. Bipolar Disord. 2017 Sep 12.
 Cipriani A. et al. Lithium in the prevention of suicide in mood disorders: updated systematic review and meta-analysis. Database of Abstracts of Reviews of Effects (DARE). 2013.
 Lewitzka U. et al. The suicide prevention effect of lithium: more than 20 years of evidence—a narrative review. International Journal of Bipolar Disorders. 2015;3:15.
 Albert U. et al. Lithium treatment and potential long-term side effects: a systematic review of the literature. Riv Psichiatr. 2014 Jan-Feb;49(1):12-21.