Then you could just look at emergency admissions where the patients were brought in after self-harm attempts that left them obviously in need of immediate medical attention. Unless you're going to suggest our standards for judging whether someone might bleed to death (for example) have changed noticeably in recent decades. Seems to me the idea that teens today are no different to those of prior generations, we're just better at noticing when they've self-harmed (or indeed, committed suicide) and more likely to attribute that to mental health issues is at best wishful thinking, and at worst dangerously dismissive.