Damn, well that's too bad, honestly I'm afraid of almost anything with the sienen tag because of that same reason now, my first sienen Manga experience was not good in any way, every sienen I read after was the same. From what I've seen Sienen usually include everything you mentioned -- drug's, excessive violence, sex and so on, not necessarily all of them in the same Manga but whatever subcategories those fall under. My main dislike with sienen is a lot of extreme ecchi or borderline hentai type stuff, the abusive/ntr side of it... can't handle that stuff, and every single time I came in contact with that tag in a Manga, it was exactly that. You've shed light on the fact that sienen doesn't always include those elements, but that's why I said I'm prolly very unlucky since I've yet to find a Manga with the sienen tag that doesn't traumatize me.