Cory Monteith ODs On Heroin And Alcohol Despite Lea Michele Love And Support: Why Did Rehab Fail Him?

Since Cory Monteith's passing on July 13, the British Columbia Coroners Service has declared the "Glee" star died from "mixed drug toxicity" involving heroin and alcohol.

"Our belief is that when he took the heroin he was alone," says Vancouver Police Department spokesman Brian Montague according to Fox.

"There was evidence in the room that was consistent with a drug overdose. We're not providing exactly what we found at the scene."

Sadly, this comes on the heels of a recent stint in a treatment facility in April for substance addiction.

Since the death of Cory Monteith, his on-screen, off-screen girlfriend Lea Michele has been grieving the loss with her family.

"Lea is deeply grateful for all the love and support she's received from family, friends, and fans," says an official statement.

Since Cory's passing, Lea has been grieving alongside his family and making appropriate arrangements with them. They are supporting each other as they endure this profound loss together."

But why did the 31-year-old's rehab treatment fail?

"One of the main reasons death can occur shortly after an individual is released from rehab is because of a large decrease in tolerance that their body experiences after a period of abstinence," says Alternatives Addiction Treatment Center research director Dr. Adi Jaffe.

"If they return to using, they might experience far more extreme reactions to drug doses they were once accustomed to using."

Monteith had publicly discussed his struggles with drug addiction, including heroin and alcohol. Reportedly, his first stint in rehab occurred at 19 after his family and friends staged an intervention.