I know of ten, and that is just among people I knew well enough to know the details, (that they were carted off to the psych ward for treatment as in completely not coping). That does not include the slew of others I know who were on anti-anxiety and depression medications but still functioning on some level and no trip to hospital (or they kept it quiet enough no one knew).
To be fair, most who had a complete breakdown were victims of abuse of some sort. I also knew many who were self medicating depression and anxiety with alcohol
I also know of three suicides and a couple of attempted teen suicides. Oh if you include the attempted teen suicides, you can bump my previous number to 12.
Such a happy bunch.