Why is Hollywood depressed?

Since the death of cherished actor and comedian Robin Williams, August the 11th 2014, people have begun to question; What is it about Hollywood that leads the stars to such tragic and sometimes intentional deaths?
For Robin Williams his death was a suicide: asphyxiation. He had suffered from a long history of depression and alcohol addiction. 

However he was one of the most talented actors of the Silver Screen and was an Oscar-nominated performer. These stars seem to have eveything we are tought bring us hapinness from an early age: money, power and glory.
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Other stars with Worldwide success linked to depression and addiction are (to name only a few): Anne Hathaway, Angelina Jolie, Jim Carrey, Catherine Zeta-Jones, JK Rowling, Brad Pitt, Kurt Cobain, Peaches Geldolf, Amy Winehouse, Demi Lovato, Brooke Shields, Billy Joel and Ashley Judd.

Let us not forget the first stars of Hollywood's Golden era who first encountered the emptiness of fame, when Elizabeth Taylor was checking into depression clinics, and Judy Garland and Richard Burton where battling alcohol addiction, a disease which would eventually kill them.
 Drew Carey, known for The Drew Carey Show and Whose Line Is It Anyway?, has also recently confessed that at the age of 18 and in his 20s he tried committing suicide. He confirs that life in Hollywood is alienating and does not allow people to go and seek out help when they need it.

If it's not alcohol dependancy or depression, unfortunately there's over-the-counter drugs. From Marilyn Monroe to Heath Ledger, Michael Jackson and the recently deceased Philip Seymour Hoffman. Hollywood's limelight seems to have a short shelf-life and tragic ending for all.