The office also explained to Entertainment Tonight that "other undermined factors" contributed to the actress' death, but sleep apnea was the main cause.
Fisher had a heart attack December 23 while on a flight from London to Los Angeles, and died several days after.
Her mother and fellow Hollywood icon Debbie Reynolds died a day later, after being rushed to hospital, aged 84. Additionally, he told the site, "I am not shocked that part of her health was affected by drugs", noting prescriptions she took to treat her mental health.
According to the press release, Fisher's cardiac arrest was caused by multiple drug intake, with "significance not ascertained".
The agency did not immediately respond to a request for additional details about whether a full autopsy report and toxicology results were available.
And while the coroner's report may insist that it was a myriad of causes that contributed to her death, her self-suggested line of "drowned in moonlight, strangled by her own bra" has always seemed way more fitting.
Todd Fisher, her brother, said he wasn't surprised.
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The first of those surprises, the "Super-Duper Graphics Pack", will be downloadable "this fall" as a free upgrade for the game . Saved data, purchased content, and world progress will transfer over from the older versions of the game to the new one.
She said she smoked marijuana at 13, used LSD by 21 and was diagnosed as having bipolar disorder at 24.
After undergoing treatment in the mid-1980s for cocaine addiction, Fisher wrote the bestselling novel "Postcards from the Edge", about a drug-abusing actress forced to move in with her mother. "She was treated with electroconvulsive therapy and medication".
"If you want to know what killed her, it's all of it". Let's celebrate not doing them by doing them.' I got into trouble each time. "Can you really blame them?" he said.
"Without her drugs, maybe she would have left long ago".
Fisher made her feature film debut opposite Warren Beatty in the 1975 hit Shampoo.
Fisher will be seen later this year in "Star Wars: Episode VIII - The Last Jedi".