Nearly three months after Margot Kidder was found dead at her home in Montana, the actress' death has been ruled a suicide by overdose.
In a statement released to ET by Park County coroner Richard Wood, it was announced that Kidder "died as a result of a self-inflicted drug and alcohol overdose." The coroner said no additional details would be released.
"Ms. Kidder’s family urges those suffering from mental illnesses, addiction and/or suicidal thoughts to seek appropriate counseling and treatment," the statement added. "The public is encouraged to allow the family to grieve privately."
At the time of her death, Kidder's manager, Camilla Pines, told ET that the actress died "peacefully in her sleep" on May 13. She was 69.
Maggie McGuane, the Superman actress' daughter by ex-husband Thomas McGuane, said that it is "a big relief that the truth is out there" in an interview with the Associated Press. "It’s important to be open and honest so there’s not a cloud of shame in dealing with this."
Kidder is best known for playing intrepid reporter Lois Lane opposite the late Christopher Reeve in 1978's Superman. She reprised the high-profile role in the three more films in the franchise. Additional high-profile roles included her part in 1979's The Amityville Horror and 1975's The Great Waldo Pepper, opposite Robert Redford.
Kidder was famously outspoken and candid about mental illness and her struggles with bipolar disorder after making headlines in 1996 when she disappeared for four days and was found in a backyard in Glendale, California. Kidder later said she suffered a manic episode.
Kidder is among a number of celebrities who have died from suicide this year, including celebrity chef and TV personality Anthony Bourdain, EDM producer Avicii, and fashion designer Kate Spade.
Reflecting on her mother's death and the high rates of suicide in the United States, McGuane said, "It’s a very unique sort of grief and pain… Knowing how many families in this state go through this, I wish that I could reach out to each one of them."
For a look back at Kidder's inimitable life and legacy, watch the video below.
If you or someone you know needs help, please call the National Suicide Prevention Lifeline at 1-800-273-TALK (8255).
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