Rocker Steven Tyler checked himself into drug rehab earlier this week, and now sources close to the star are saying that his stormy relationship with his girlfriend may be to blame.

The Boston Herald said on Thursday that Tyler's friends have said that his relationship with Erin Brady may be part of the reason for his relapse. The pair have been on-again-off-again for two years.

But other sources think that Tyler's various health issues in recent years may have led to dependence on pain killers.

One of his friends said, "He's had throat surgeries, a long bout with hep(atitis) C and two foot surgeries. He's been in a lot of pain. And she's a party girl. Not a good combination."