The New York City medical examiner released the final autopsy report. Cause of death: a combination of six prescription drugs. Ledger "died as the result of acute intoxication by the combined effects of oxycodone, hydrocodone, diazepam, temazepam, alprazolam, and doxylamine."

The accidental death resulted "from the abuse of prescription medications."

In Ledger's case, CNN learned that the combination of drugs probably caused his central nervous system to slow down so much that his heart stopped beating and lungs stopped breathing and he never woke up.

Even though no illegal drugs had been found in Ledger's apartment, two unnamed law enforcement officials told the Associated Press that six types of prescription drugs were found.

It's hard to imagine that any doctor would prescribe all six of these drugs to the same patient, but nowadays it's not difficult to obtain prescriptions from several different doctors.

A spokesperson for the medical examiner tells us that none of these drugs - two sleep medications, two anti-anxiety drugs and two narcotic painkillers - was taken in excess.

Many people may not realize that mixed together, sleep aids, anti-anxiety drugs, antidepressants and narcotic painkillers can be lethal.

Some use prescription drugs to get high because they are so widely available, and much easier to get than illegal drugs such as cocaine and heroin.

And many parents may not know that among teens, prescription drug abuse ranks ahead of all illegal drugs except for marijuana according to a report by the White House Office of National Drug Control Policy released two days after Ledger's death.

Many, including Ledger's parents, hope that lessons will be learned from this tragedy. In a statement, the family said, "Heath's accidental death serves as a caution to the hidden dangers of combining prescription medication, even at low dosage."