Anna Nicole's second autopsy

Model Anna Nicole Smith and her son Daniel Smith are shown at G-Phoria - The Award Show 4 Gamers on July 31, 2004, in Los Angeles. Daniel died Sunday, Sept. 10, 2006, at the hospital in the Bahamas where his mother gave birth to a baby girl three days before. Authorities had not determined what caused the death of the now 20-year-old, but authorities reportedly do not suspect foul play. (Photo: GETTY IMAGES/Frazer Harrison)

Controversial formerPlayboyplaymate Anna Nicole Smith's son was on prescription anti-depression medication when he died at the hospital bedside of the former reality TV star, a pathologist who did a second autopsy on the 20-year-old Daniel Smith said today.

Forensic pathologist Cyril Wecht said Daniel Smith was being treated for depression that began about four to six weeks earlier but he did not know whether the medication played any role in his death, which came three days after his celebrity mother gave birth in the Bahamas.

Wecht, speaking by phone from the Miami airport a day after conducting the autopsy in the Bahamas, said he's awaiting toxicology tests to determine the cause of death.

He said he and the Bahamian coroner who did the first autopsy agreed there is no evidence Daniel Smith died from a "suicidal overdose".

Smith died on September 10 in the hospital room where the former Playboy model was recuperating from giving birth to a daughter.

Wecht said he spoke to the psychiatrist who treated Daniel Smith, and was told the dosage of the antidepressant medication - which he declined to name - was "quite low" and that the depression "had to do with a girlfriend".

"The doctor was very surprised. He couldn't explain what could have gone awry," he said of the psychiatrist.

He did not provide further details and said others, including Anna Nicole Smith's lawyer Howard K Stern, said Daniel Smith had seemed to be in good spirits in the days before his death.

"He was delighted. He was happy to be there with his mother and his sister," Wecht said.

Earlier, Wecht had said the autopsies have ruled out several natural causes and the results of the drug and chemical analyses could take weeks to complete. Investigators have said they did not find evidence of drugs in the room or obvious signs of a crime.

Wecht, who gained fame as a consultant on celebrity cases including Elvis Presley's death, ruled out several potential natural causes, including heart disease, stroke or a "congenital anomaly", and said there was no indication of foul play.

"I don't find anything that would cause me to believe there is something in terms of some traumatic injury having been inflicted, or somebody having done something to him in some cryptic manner that could not be observed," he said.

Bahamian pathologists performed an autopsy Tuesday and were expecting toxicology results this week, but the coroner's office has said the findings will not be released before a jury inquest scheduled for Oct. 23 to determine the cause of death.