Nov. 18, 2002 -- President John F. Kennedy's medical records reveal that he had suffered health problems since childhood, and used an arsenal of drugs, including painkillers and stimulants, to treat various medical conditions during his presidency.

A historian who examined his medical records was stunned at the extent of the health problems that the seemingly vigorous president dealt with.

"There was hardly a day that went by that he didn't suffer terribly," presidential historian Robert Dallek, a history professor at Boston University, told ABCNEWS' Good Morning America.

The revelations about JFK's health are included in Dallek's forthcoming book, An Unfinished Life: John F. Kennedy, 1917-1963, which is excerpted in the December issue of Atlantic Monthly. Dallek was granted exclusive access to Kennedy's private papers for the years 1955 to 1963, including his X-rays and prescription drug records.

Kennedy suffered from colitis, prostatitis, and a disorder called Addison's disease, which affects the body's ability to regulate blood sugar and sodium. He also had osteoporosis of the lower back, causing pain so severe that he was unable to perform simple tasks such as reaching across his desk to pull papers forward, or pulling the shoe and sock onto his left foot, Dallek said.

Taking Drugs During Crises

To fight the pain, Kennedy took as many as 12 medications at once, taking more during times of stress.

The medical records reveal that Kennedy variously took codeine, Demerol and methadone for pain; Ritalin, a stimulant; meprobamate and librium for anxiety; barbiturates for sleep; thyroid hormone; and injections of a blood derivative, gamma globulin, a medicine that combats infections.

During the Bay of Pigs fiasco in 1961, and the Cuban Missile Crisis in October 1962, Kennedy was taking steroids for his Addison's disease, painkillers for his back, anti-spasmodics for his colitis, antibiotics for urinary tract infections, antihistamines for his allergies, and on at least one occasion, an anti-psychotic drug to treat a severe mood change that Jackie Kennedy believed was brought on by the antihistamines.

This deluge of drugs often had side effects, including grogginess or even depression. To treat this Kennedy took more still anti-anxiety medications. Yet, there is no indication that the medications impaired JFK's judgment during crucial moments in U.S. history.

"I studied very closely his performance during these crisis, and what was striking is how effective he was," Dallek said. "He made a bet with himself and the country, in a sense, that he could be president, and he carried it off brilliantly. It was extraordinary."

Hiding the Pain

But Kennedy and his closest circle took great pains to hide his health problems from the public, fearing it would impair his political career. JFK was particularly fearful that revelations about his health problems would hurt him in the neck-and-neck presidential race with Richard Nixon in 1960.

He was so terrified of his medical conditions being known that in the 1960 fight for the Democratic nomination, Lyndon Johnson aides aired the fact that Kennedy had Addison's disease, and the Kennedy campaign flatly denied it, Dallek said. His doctors later published a letter saying his health was excellent.

As amazing as the list of drugs Kennedy took is the fact that it was kept mostly secret. To this day, his closest aides don't know or won't admit the extent of his ailments.

"He was a man in very good health," said Kennedy adviser Ted Sorenson told ABCNEWS. "There is no doubt about the fact that he had a bad back, as millions of men do, sometimes it hurt worse than others."

His aides attributed any visible problem to a war injury. When the president rode a cherry picker to board Air Force One, it was just because of a sore back, not the fact he couldn't climb a stair.

In the book, Dallek speculates that the corset Kennedy wore for his back trouble may have made him a sitting target for his assassin, Lee Harvey Oswald. Kennedy's back was ramrod straight, making his head and neck perfect targets when the second bullet — believed to be the one that killed him — struck.

"Of course we'll never know, but if he had toppled over when the first bullet hit, he might have been saved," Dallek said.