Coroner's officials said the death of Marie Osmond's son was ruled a suicide and that drugs or alcohol did not play a role in the teenager's fall from a balcony.
Authorities suspected that Michael Bryan killed himself by leaping from an eighth-story balcony in Los Angeles in February.
The 18-year-old college student left behind a suicide note, but the coroner's office wanted toxicology results before ruling on his cause of death.
Mr Bryan was one of five children that Osmond and her ex-husband adopted.
Osmond and her brother, Donny, took a brief break from their Las Vegas show before returning with a teary tribute to Bryan in March.