Stress can also be a factor.
A former coworker of mine was on a high profile team assigned to revamp the entire scheduling, estimating and materials programs. His ideas were ignored by the rest of the team and he got steamrollered. Any time he raised an objection or suggested an alternative, he was told, "Our hands are tied. We can't do it.".
Late Friday a little over a year ago, he hanged himself in the executive conference room. His hands were tied together.
Obviously, in his mind, he was sending a message. Management hushed everything up and swept it under the rug. They ended up spending about $500 million on a new system that, at this point, doesn't work near as well as the old system. Message ignored.
There is NOTHING at the company worth killing yourself over. In his case, he had been to counselling, but (obviously) still had unresolved issues.