Kenneka Jenkins' cause of death was hypothermia and "cold exposure in a walk-in freezer" as well as "ethanol and topiramate intoxication," the Cook County Medical Examiner's Office said.
Topiramate is prescribed for a range of conditions, but is most commonly used to treat epilepsy and migraines.
Jenkins, 19, was last seen early Saturday, September 9, at a party at the Crowne Plaza Chicago O'Hare Hotel.
Her family reported her missing later that day, and Jenkins' body was found in the walk-in freezer at the hotel shortly before 1 a.m. on Sunday, September 10.
The medical examiner said an autopsy found stomach lesions indicative of hypothermia, an abrasion on Jenkins' right ankle and a bruise on her right leg.
"There was no other evidence of external or internal trauma," the office said.
It said comprehensive toxicology tests for "hundreds of drugs of abuse, medications and other chemical compounds" -- along with date-rape drugs -- were carried out but none were found.
The level of topiramate was found to be within appropriate prescription levels, but Jenkins' family said she had not been prescribed the drug, the office said. Jenkins also had levels of alcohol higher than the driving limit.
"When combined, the effect of either or both drugs is enhanced. Topiramate, like alcohol, can cause dizziness, impaired memory, impaired concentration, poor coordination, confusion and impaired judgment. Central nervous system depression, or impairment, combined with cold exposure can hasten the onset of hypothermia and death," the release said.
The forensic pathologist assigned to the case and the medical examiner's chief of investigations -- a former homicide detective lieutenant -- conducted a follow-up investigation at the hotel on September 27, it said.
'Manner of death: Accident'
They retraced Jenkins' path, ending at the cooler that contained the freezer where her body was found.
"The cooler and freezer were both outfitted with external handles that must be pulled to open. The inside of the freezer door was equipped with a circular release mechanism," the office said.
It said there were no other doors giving access to the back of the kitchen where the cooler was located.
Security camera footage provided by the police showed Jenkins entering the kitchen at approximately 3:32 a.m. on the Saturday. The footage does not show her entering the cooler and freezer because no cameras show the doors directly. Jenkins was discovered approximately 21 hours after entering the kitchen, the office said.
"There is no evidence, per the police investigation, that Ms. Jenkins was forced to consume the alcohol or the drug. There is no evidence of another person in the vicinity of the kitchen with the decedent and there is no evidence of an altercation or interaction with another individual in the time immediately prior to demise," it said. "There was no other evidence of external or internal trauma due to physical abuse.
The medical examiner's office concluded that the cause of Jenkins' death was "hypothermia due to cold exposure in a walk-in freezer. Alcohol and topiramate intoxication are significant contributing factors. The manner of death is: Accident."
Surveillance video from inside the Crowne Plaza, released by the Rosemont Public Safety Department and obtained by CNN, showed Jenkins staggering through the hotel's hallways early Saturday before she disappeared.
When her friends realized Jenkins was missing, they notified her mother, Tereasa Martin. In recordings of 911 calls released by the police and obtained by CNN, Martin said the friends her daughter was with had gone upstairs to find a phone and left Jenkins in the hotel's lobby.
When they came back, Martin said, Jenkins was gone. Martin told the police dispatcher that her daughter's friends said she drank "one cup" but that "one cup is too much for her," Martin said.
Her death sparked accusations on social media of foul play and the Rosemont Public Safety Department said it was publicly disclosing all the video surveillance from the Crowne Plaza Hotel that showed Jenkins the night of her disappearance.
Jenkins' mother and her attorneys last month criticized the hotel's response.
Martin, the attorneys said, called the hotel and went there early Saturday to ask them to review surveillance footage to find her daughter. They allege the hotel never checked or searched.
According to CNN affiliate WBBM, a hotel spokesman, Glenn Harston, said Jenkins' death was "a tragic accident."