I know two people, the specific relationships are not anyone's business.
One tried to kill them self. The other experienced suicide idealization while in middle school.
Both are now on small does of Risperidone. The Psychiatrist stated that this was a result of a chemical malfunction in the brain. He further stated that the brain is an organ just like anything else. "Mental Illness" is an artificial moniker given to a set of conditions that physicians are just now beginning to fully understand. It is no different than any other medical condition.
And sure, you can develop medical conditions as the result of work conditions...lack of sleep and stress can give you high blood pressure which can lead to strokes, kidney failure, etc. Should Uber or any other company be held liable for that too?
With respect to depression, it can also be brought on by lack of sleep. Sleeping is a required function of the brain. You sleep for a reason...physiological reasons. That's why people with sleep disorder diseases can die without sleep.