Without putting either on the spot /u/bfg_foo &/or /u/baronzaterdag who specialise in Media history (amongst other things) might have an answer you. In the meantime you could check out these links from a variety of suicide prevention & academic institutions from around the world:

• Suicide.org's "Media guidelines for suicide reporting"

• Samaritans's "Media guidelines for the reporting of suicide"

• Mind Frame's "Suicide in the media"

That's a really interesting question. I'm not aware of a lot of research on this question but Gemma Richardson looked at media coverage of suicide in two Canadian newspapers from the mid-nineteenth century until the end of the twentieth century. Her finding was that, in Canada at least, the taboo against reporting on the suicide of ordinary people, now in decline, only emerged in the mid-twentieth century. In the nineteenth century, reports on suicides were often quite explicit detailing names, methods used, attributing causes, reproducing suicide notes, etc. According to Richardson, the emphasis on suicide reporting in the first half of the twentieth century switched to a focus on the bizarre, sensationalist or high profile rather than the everyday. From the mid-twentieth century, she argues, the medicalisation of suicide and its linkage to depression together with the professionalisation of journalism led to greater reticence in the reporting of everyday suicide and the increasing use of euphemism.

Actually media guidelines from medical organisations and mental health groups on suicide reporting appear to be largely early 21st century products and are, according to Richardson, based upon a questionable reading of the existing research literature on suicide contagion.

Anyway, forgive my inadequate summary of Richardson's thesis but I'm not aware of any other research directly addressing this question.

You can look at her thesis here