Mental illness takes many forms & is still not fully understood, some forms are known to be caused by a Chemical imbalance,
These people cannot help themselves or shake it off if they could don't you think they would?
Also the very drugs that are used to treat the depression often have the side effects in the first weeks of making the depression so bad that suicide is a real threat.
No one who is close to a depressive can help them , only encourage & hope they will eventually come out of this dark place they are in.
Cocaine taking when on anti depressive only exacerbates the condition, a massive high followed by an even worse low.
Many of these brilliant comics suffer from what has now been found to be bi polar, Spike Milligan, Peter Sellers, & so on.its well documented
It's very sad, he gave pleasure to many but his inner torment was such that in a moment of being in the grip of this he committed suicide, it has been found that no alcohol was involved.i don't know if they've found evidence of illegal drugs, either way the end for him was inevitable at some point!.