He does work in a lab with serious compounds, but I have since been told by a member of his crisis team that they know about previous (relatively minor) mental health incidents in his past. I was completely unaware of this, so I am assuming he has dealt with this on his own for a long time, until he was unable to anymore.

I am near certain he is not a drug user either. I have never seen any evidence of this, and in my experience drug addicts are not very good at hiding it when they lose control.

Also, I contacted his work abbout his absense (without details) from my own phone. His colleague (boss?) called me back because they were already concerned about him late last week at work. If they suspected something concerning the work they do, they would have told me or the hospital.