Authorities have determined that Saoirse Kennedy Hill, the 22-year-old granddaughter of assassinated presidential candidate Robert F. Kennedy, died of a drug overdose. The Boston Globe and WCVB-TV reported Friday that a toxicology test found methadone, fluoxetine, norfluoxetine, diazepam, nordiazepam and alcohol in her system.

Fluoxetine is an antidepressant, and diazepam is used to treat anxiety and alcohol withdrawal symptoms.

Hill was found unresponsive at a home at the Kennedy compound on Cape Cod on Aug. 1. She was pronounced dead at Cape Cod Hospital. Hill was scheduled to start her senior year at Boston College this fall.

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She was the daughter of Robert and Ethel Kennedy's fifth child, Courtney, and Paul Michael Hill.

Hill had written frankly and publicly about her struggles with mental health and a suicide attempt while in high school. In an op-ed for her high school publication nearly a decade later, Saoirse described her struggles.

"My depression took root in the beginning of my middle school years and will be with me for the rest of my life. Although I was mostly a happy child, I suffered bouts of deep sadness that felt like a heavy boulder on my chest. These bouts would come and go, but they did not outwardly affect me until I was a new sophomore at Deerfield," she wrote.