Park County coroner Richard Wood said in a statement released today that Kidder "died as a result of a self-inflicted drug and alcohol overdose" and that no further details would be released.
Kidder played the intrepid reporter Lois Lane opposite Christopher Reeve's Man of Steel in four Superman films from the 1978 original to 1987's Superman IV: The Quest for Peace. The Coroner has not specified what drugs she took.
She continued to act in her later years but her popularity waned after she suffered a highly publicised mental breakdown in 1996.
Texas student takes grad photos with 14-foot alligator
Noland wore her school colors, Texas A&M sash and graduation cap for the shoot, which took place in the middle of Big Tex's swamp. Noland said she'll graduate Friday in College Station, and she hopes to find a job at a zoo in the Dallas-Fort Worth area.
"It's a big relief that the truth is out there", the daughter, Maggie McGuane, said.
Now, nearly three months after Kidder's body was found by a friend in her Livingston, Montana home, a coroner there has ruled her death a suicide.
In what was an obvious reference to the Superman movies, Kidder made a cameo in Smallville along with the series' stars Michael Rosenbaum and Allison Mack. I want what I know about her to be out there because it was glorious.
And she was known for her work as a mental-wellness advocate, in part because of her own struggles with mental health. A friend discovered Kidder's body at her home on May 13th. Her film "Robber's Roost" was in pre-production, and the final film she worked on was 2017's "The Neighborhood".