The fashion designer, whose LS Fashion brand was losing millions of pounds, was discovered on Monday morning at the upmarket Manhattan tower block.
A spokeswoman for the Chief Medical Examiner of New York City's office confirmed the cause of death.
The stylist and former model had been due to close down the company as friends revealed she had become increasingly troubled about its financial problems.
Latest accounts showed that despite her success as a catwalk model LS Fashion lost £3.6 million in 2012. She also reportedly owed creditors £4.6m.
Miss Scott's clothes were worn by Hollywood stars such as Nicole Kidman and American First Lady Michelle Obama.
Sir Mick, who had been dating Miss Scott for 13 years, is thought to be in America, where preparations for her funeral are taking place. A spokesman would not say what arrangements were being made.
The Rolling Stones had been in Australia preparing for a gig in Perth when Sir Mick learned of the tragedy and the group have since called off their tour, which included New Zealand.
Before departing Australia, Sir Mick wrote of his distress and sorrow about her tragic death in a website blog.
He said: "I am still struggling to understand how my lover and best friend could end her life in this tragic way She had great presence and her talent was much admired, not least by me."