Actress Margot Kidder, best known for her portrayal of Lois Lane in the ?Superman? films passed away in Montana in May. According to Extra, the Park County Coroner has determined the cause to be death by suicide. According to the coroner's report, the actress died as the ?result of a self-inflicted drug and alcohol overdose.? It is unknown which drugs she ingested. Her daughter Maggie McGuane, 41, told the wire service that she already knew that her mother, who had battled bipolar disorder during her lifetime, had died by suicide saying, ?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.?