Melanie Anne Elizabeth Garrison, 18, was found unresponsive in her bed by her parents on May 24, the day after she graduated from Lakeside High School.
She died of natural causes, Columbia County Coroner Vernon Collins said.
Miss Garrison died from hypertension, cardiovascular artery disease and obesity.
Mr. Collins said Miss Garrison had spent the night after graduation with a friend and returned home May 24 while her father and stepmother were out.
Mr. Collins said he wanted to wait until lab results were in before determining Miss Garrisons cause of death. Those results were only recently received and he signed Miss Garrisons death certificate Wednesday.
She was clean, Mr. Collins said. She had no drugs in her system at all.
Reach Valerie Rowell at (706) 868-1222, ext. 110 or