The autopsy, conducted by the Orlando, Florida, Office of the Medical Examiner on June 7 and released Wednesday, found a significant concentration of both drugs in Siegel's system. Methadone is used for pain treatment, and Sertraline, better known as Zoloft, treats depression. The Medical Examiner also found linear scars of up to 5 cm. on the inside of the teenager's left wrist. The death has been ruled an accident.
Siegel, who died on June 6, long struggled with an addiction to prescription drugs that she initially began taking for a seizure condition, according to family spokesperson Michael Marder.
"Unfortunately she became dependent and struggled with this condition," Marder previously told PEOPLE. "She voluntarily underwent rehabilitation and was working hard to address this problem."
The family said in June that it was likely Victoria had ingested one or more drugs prior to her death, but were unsure what they were and how they were obtained until the toxicology report was finalized.
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"The ex-girlfriend of Victoria's boyfriend used his phone to send cruel and hateful text messages using the boyfriend's phone," Marder said through a Facebook statement last month. "These messages were sent early on the morning of Victoria's death. These messages were clearly intended to hurt Victoria and while we cannot be sure may have affected her emotional state at a time when she was emotionally vulnerable."
For an exclusive interview with Jackie and David Siegel, check back on PEOPLE.com tomorrow