Why did Adam Gontier take Oxycontin?

Adam Gontier stated on Behind the Pain that he got addicted to Oxycontin by seeing a friend that supplied it.

He met the friend at a party, and he was handing out the pain killers, and Adam Gontier took one. He said that it made him feel so good that he asked his friend for more the next time he saw him. Eventually it became an addiction.