"Mr. Kinkade died of respiratory depression as a result of a high concentration of ethanol combined with benzodiazepine use," said the report, which was released Monday.
NBC Bay Area News said Kinkade's April 6 death at his Monte Sereno home has been categorized as an accident involving alcohol and valium.
His brother, Patrick, told the San Jose (Calif.) Mercury News Thomas battled alcoholism for years and suffered a relapse in his sobriety shortly before his death at age 54.
Notable deaths of 2014 [PHOTOS]
Reports: Mila Kunis gives birth to baby girl