Mary Richardson Kennedy, 52, had trazodone, venlafaxine and desmethylvenlafaxine in her system when she killed herself in a barn at her family's estate in Bedford, according to the Westchester County Medical Examiner's report.
Kennedy's divorce from Robert F. Kennedy Jr. was pending at the time of her death, and one of her brothers tried unsuccessfully to get custody of her body before she was buried near the Kennedy compound in Massachusetts.
Kennedy Jr. didn't immediately return a call seeking comment Friday.
In divorce papers, her husband - son of U.S. Sen. Robert F. Kennedy and nephew of President John F. Kennedy - had asked that she be required to remain sober in front of their four children and not threaten suicide in their presence. Her family accused him of using the filings as a "brutal psychological weapon."
Mary Kennedy's internal struggles became public after she and her husband split. She was arrested twice on charges of driving while intoxicated.
"She struggled so hard, for so long, with mental illness, which so many Americans suffer with," said Kerry Kennedy, her sister-in-law and nearly lifelong friend. "She fought with dignity, and in the end, the demons won."