The cause of death for Margot Kidder, best known for portraying Lois Lane in Superman: The Movie opposite Christopher Reeve, has been revealed.
On Wednesday, coroner Richard Wood of Montana’s Park County Coroner’s office confirmed to the Associated Press that Kidder’s death was “a result of a self-inflicted drug and alcohol overdose.”
A representative for the Park County Coroner did not immediately respond to PEOPLE’s request for comment.
After Kidder’s cause of death was revealed, the star’s only daughter, Maggie McGuane, told the AP, “It’s a big relief that the truth is out there. It’s important to be open and honest so there’s not a cloud of shame in dealing with this.”
Kidder’s struggle with bipolar disorder, which became highly publicized after a 1996 manic episode left her homeless for a time.
Kidder told PEOPLE five months after the incident that the root of most of her problems — which include “mood swings that could knock over a building” — was bipolar disorder. She was first diagnosed with the condition by an L.A. psychiatrist eight years prior, but she refused to take the recommended prescription of lithium, the recommended treatment.
After receiving treatment, Kidder went on to become a lifelong advocate for mental health awareness.
