I'm not sure why, but if I had to speculate: acceptance of mental healthcare grew substantially in the 90s (including meds), anti-suicide/intervention programs, anti-bullying campaigns (especially after Columbine). Also, any time I see a graph with any kind of dip around 9/11, I wonder if that major cultural shift had any effect.
As for the steep rise again, I think it's simply social media.
You could also argue that the sharp rise occurred around 2008 with the market crash. I bet a lot of families got broken after the housing bubble burst.
There is a slight uptick around 2002 as well which could correlate to 9/11
Not to AKSHUALLY so much but I think that second inflection point is more in line with Facebook removing the .edu email requirement. As horrible as Vista was, I do think credit should be given there. PS1 release tracks tho.