"The decedent would have vertigo to the point of vomiting, but she learned to control the symptoms with antihistamines," the report stated.
The drug Adderall had been prescribed to Rivera for anxiety and was recently taking medication for a sinus infection. Additionally, Rivera "used a marijuana vape pen and she would smoke about a pack of cigarettes per week", the report stated.
Rivera had "no known history of suicidal ideation or attempt".
It is also thought the actress was a "good swimmer" and the cause of her death remains as a drowning.
The manner of death was ruled as an accident.
The Ventura County Medical Examiner also released Rivera's toxicology report.
It revealed Rivera had low-level amounts of amphetamine (Adderall, Dexedrine), diazepam, ethanol and phentermine (an appetite suppressant) in her system, as well as caffeine, at the time of her death.
According to the toxicology report, her blood alcohol concentration was 0.016.
"[Naya's] cell phone, syringes with a pink fluid substance, identification, and a filled prescription slip for amphetamine was found in [her] purse. Three 12-ounce White Claw alcohol cans were located near [her] purse. One of the cans was empty, one was open and was about three-quarters full, and one was unopened. There was a bag with food items on a bench seat near the front of the boat."
Rivera was confirmed dead on July 13 at the age of 33, which was five days after she was reported missing.