From a BBC report...
Drug abuse and suicide seem to have a pretty strong correlation with one another, as evidenced by the countless list of celebrities with well-known chemical addictions who have taken their own lives. Drugs tend to amplify emotions and many of them thin-down a person's apprehensions and prohibitions toward behavioral extremes and risky, sometimes fatal, activities.
While I am not saying that Bourdain was strung out when he allegedly took his own life, I am saying that there is a lot of evidence substantiating the fact that once you chemically uncage certain emotional demons, a person might never be able to successfully put them back in their box and can fall victim to them much later in life. Even when sober.
It's sad.
If you know someone struggling with depression, help them get help. They may not want it and may not accept it, but try.