Perry, who was best known for playing wise-cracking Chandler Bing in Friends, was found unresponsive in the swimming pool at this home on 28 October and pronounced dead at his LA home.

Other contributing factors to his death included drowning, coronary artery disease and the effects of buprenorphine, which can be used to treat opioid use disorder, the post-mortem said.

Ketamine is a sedative that can be used as a recreational drug, as well as to treat depression.

A report from the Los Angeles Department of Medical Examiner stated that Perry was "receiving ketamine infusion therapy for depression and anxiety" with the most recent dose reportedly taken one and a half weeks before his death.

The report continued: "The ketamine in his system at death could not be from that infusion therapy, since ketamine's half-life is three-to-four hours, or less."

Read more:
What Perry's memoir revealed
Obituary: The one who made everyone laugh
Perry's life in pictures

Perry, 54, appeared in the hit US show, which is set in New York between 1994 and 2004.

Tributes poured in for Perry in the days after his death, including from his co-stars.

Friends actors Matt LeBlanc, Jennifer Aniston, Courteney Cox, David Schwimmer and Lisa Kudrow, were also among the 20 mourners at Perry's funeral in the Hollywood Hills in November.

Perry was open about his battle with substance abuse and addiction, and set up a sober living facility for men with similar issues.

A foundation has now been set up to help others struggling with the disease in his memory.

Aniston, who played Rachel Green in the sitcom, was among those urging support of the foundation which was set up to "honour his legacy".

Perry's cause of death comes days after Aniston revealed she had been messaging him on the morning of his death, describing him as "happy and healthy".

"I want people to know he was really healthy, and getting healthy. He was on a pursuit. He worked so hard. He really was dealt a tough one," she told Variety.