A statement provided by the coroner to The Associated Press said that Kidder had "died as a result of a self-inflicted drug and alcohol overdose".
While no further details will be released of her suicide, McGuane added that "it's a unique sort of grief and pain and that she would like to reach out to every family who is suffering through a loss by suicide".
Kidder's daughter, Maggie McGuane, told the publication on Wednesday that she knew her mother had died by suicide when she went to her home in Livingston, Mont.More news: NYC reins in Uber with cap on ride-hail vehicles
The late actress, who started her career in 1968 and got her big break in the 1973 film "Sisters", starred opposite Christopher Reeve in "Superman" and three sequels. She also had two more roles yet to be released, TMZ reported. She had been struggling with bipolar disorder for years. She still helps lost animals and other causes that she's passionate about.
Her obituary in the New York Times did not specify a cause of death.
Five months after her manic incident, she opened up to People magazine saying she had "mood swings that could knock over a building".
Kidder struggled with mental illness through a good part of her life, a situation that was made worse by a 1990 auto crash that left her in debt and led to her using a wheelchair for nearly two years.More news: Veterinarians ready for efforts to save ailing orca whale
"It's very hard to convince a manic person that there is anything wrong with them", Kidder said.
Kidder was best known as her role as Lois Lane in the Superman movies in the 1980s.
But now her daughter, Maggie McGuane, has revealed that her mom committed suicide.More news: Woods trying something new at PGA Championship
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