Lisa Robin Kelly Lisa Robin Kelly

The cause of death for That '70s Show alum Lisa Robin Kelly has finally been revealed.

Kelly, who played Eric's older sister on the comedy, died from multiple drug intoxication when she passed away in her sleep six months ago, reports.

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The L.A. County Coroner has ruled the death to be an accidental overdose. The specific drugs that were in Kelly's system at the time of her death were not disclosed, but the actress had a history with illegal substances. She was arrested at least four times during the past three years for DUI, spousal abuse and assault.

At the time of her death, Kelly's agent Craig Wyckoff said that she had voluntarily checked herself into a treatment center days earlier. Kelly died on Aug. 15 at an alcohol rehab facility in L.A. County at the age of 43.

The Coroner's full report will be released within two weeks.