Disturbed minds make for good songwriting?

I've recently discovered the Swedish black/death metal band Dissection. Having never been a huge fan of guttural vocals and relentless blast beat in the first place, it was a surprise when I happened to enjoy the selection Pandora had made for me of a band with a name that cliché of black/death. The band's music is quite original, with pleasantly aggressive vocals, an almost progressive rhytm, and most importantly, for once, the quality of actually being able to hear each instrument distinctly.

The threesome, however, describe themselves as the "Anti-Cosmic Metal of Death", a satanist troup on a mission to bring the revelation to the world. But what Swedish death-metal band isn't?

The difference with this bunch is that they actually believe it. The proof? The guitar player and vocalist for the band killed himself this summer because "he felt that he had fulfilled his self-created destiny."

From the band's official website :

Jon Nödtveidt was a man who lived his life according to his convictions and True Will. A couple of days ago he chose to end his life by his own hands. As a true Satanist he led his life in the way he wanted and ended it when he felt that he had fulfilled his self-created destiny. Not everyone will have understanding or acceptance for his personal path in this life and beyond, but all must respect his choice.

Those of us who have met him in his last days can assure that he was more focussed, happier and stronger than ever. It is our full conviction that he left this world of lies with a scornful laughter, knowing that he had fulfilled everything that he had set up for himself to accomplish. The empty space that he leaves behind will be filled with the dark essence that he manifested through his life and black-magical work. His legacy and Luciferian Fire will live on through those few who truly knew him and appreciated his work for what it really was and still is. As our brother's goal in life and death never was to "Rest in Peace", we will instead wish him victories in all battles to come, until the Acosmic Destiny has been fulfilled.

For the glory of the Dark Gods and the Wrathful Chaos!

Chilling...

So, do disturbed minds make for exceptionally creative songwriting? Weren't a lot of artists from the past especially deranged, such as Van Gogh or Baudelaire? If there is a causal relationship, what direction does it take? In other words, which causes which?