The 40-year-old "killed himself while the balance of his mind was disturbed," Knapman told a public inquest that aimed to establish the circumstances surrounding his death. In Britain, inquests are held whenever someone dies violently or in unexplained circumstances.
"It seems that he had a history of self-harm and, no doubt fueled by cocaine, he resorted to desperate measures to end his life," he said.
McQueen's body was found in a wardrobe in his apartment on the eve of his mother's funeral. The coroner's court said the cause of his death was asphyxiation and hanging.
McQueen's psychiatrist, Dr. Stephen Pereira, told the inquest that the designer suffered from the pressures of his high-profile career. He was diagnosed with depression and anxiety and had attempted two drug overdoses in May and July, 2009, Pereira said.
"Usually after a show he felt a huge come-down. He felt isolated, it gave him a huge low," the doctor said, adding that the designer saw his work as a "double-edged sword."
A toxicology report said McQueen took a "substantial" amount of cocaine and sleeping pills mixed with tranquilizers prior to his death.
The designer was "overwhelmed with grief" at the loss of his mother days before he took his own life, coroner's officer Lynda Martindill said.
Police found a note that said: "Look after my dogs, sorry, I love you, Lee" scribbled onto the back of a book in his room. They said there were no suspicious circumstances.
The designer was known by his first name Lee among friends and family.
His family released a brief statement saying they were struggling to come to terms with his death.
"Today's inquest has obviously been very difficult for the family," it said. "Lee was ... a much-loved brother and son and we miss him terribly."
Known for his dramatic statement pieces and impeccable tailoring, McQueen dressed celebrities from Cameron Diaz to Lady Gaga and influenced a generation of designers.
He was named British Designer of the Year four times and awarded the title of CBE -- Commander of the Order of the British Empire -- by Queen Elizabeth II.