Carrie Fisher had heroin, cocaine and MDMA in her system when she died but their role in her death could not be determined, a coroner has found.
The full report released on Monday records her death as "undetermined" after concluding the cocaine could have been taken up to three days before she was taken ill on a flight from London to Los Angeles.
The actress Star Was, who rose to fame as Princess Leia in Star Wars, then died aged 60 in hospital four days later on December 27.
The Los Angeles acting chief coroner Dr Christopher Rogers recorded her cause of death as sleep apnoea, where breathing cuts out during slumber, and various other "undetermined factors".
He also listed arherosclerotic heart disease as a factor as well as "multiple drug use" but said its significance could not be determined.
Urine tests on her hospital admission came back positive for cocaine, methadone, alcohol and various opiates.
"At this time, the significance of cocaine cannot be established in this case," toxicologist Cyrus Rangan wrote.
Heroin, morphine and methadone were also detected but when they were taken could not be calculated.
The toxicologist noted those opiate drugs can all suppress breathing.
The expert added: "The available information is insufficient to establish the significance of opiates and opioids in this case regarding cause of death."
Coroner investigator Nani Cholakians also detailed what happened in the flight back from the UK where she had been filming on British sitcom Catastrophe.
She wrote: "Her personal assistant reported that the decedent (Fisher) was last awake and normal at the beginning of the flight.
"Throughout the flight she had multiple apneoic episodes, which was her baseline, and near the end of a 10-hour flight she was not to be aroused.
"A few minutes later the decedent vomited profusely then slumped over."
After an initial news release on Friday, Fisher's daughter Billie Lourd said she "ultimately" died of drug addiction and mental illness.
Fisher had long battled conditions such as bipolar and had become a prominent voice for those with the disorder.