What is clear is that the foursome was fond of certain drugs for years before the famous 1964 trip brought them to Ed Sullivan's studio in New York City and on stage at the Coliseum in Washington, D.C. -- and that, after their splashy U.S. debut, they weren't squeamish about trying some more.
Only the most iconoclast of cultural critics will blame the band for single-handedly making drug use cool. Even prominent members of today's socially conservative movement say that they are lifelong fans who view the Beatles' drug use in a historical context, though some critics contend that it had a lingering impact. Still, the debate continues: was their years-long trip around the substance smorgasbord a sign of the times, or did their dabbling inspire their fans to follow suit?
"People, especially teenagers and young adults, can be greatly influenced by celebrities," says Bunny Galladora, vice president of the National Woman's Christian Temperance Union.
"It is obvious that the Beatles greatly influenced clothing, hairstyles and culture in the '60s. Therefore, I would say that their drug use and the media's reporting on it also made an impact on society," Galladora says.
Russia's top anti-drug official Yevgeny Bryun famously claimed at a 2012 press conference the band "introduced the idea of changing one's psychic state of mind using drugs to the population."
Many American anti-drug campaigners declined to comment on the band's possible role in popularizing drug use.
As early as 1961, the Beatles' drug odyssey was underway with habitual use of Preludin, a stimulant, during performances at clubs in Hamburg, Germany. There they used marijuana, too, but it was only after trying it with Bob Dylan in New York City in 1964 that they got particularly high.
The first time George Harrison and John Lennon tried LSD, in 1965, a dentist in London gave them acid-infused sugar cubes without their prior knowledge. Later that year the two took it again in Beverly Hills, Calif., with Ringo Starr, but Paul McCartney opted out.
Lennon began to take the drug regularly after his first exposure.
McCartney, the last of the Beatles to try LSD, was the first to publicly admit to it during a 1967 interview with ITV. He said he used it "about four times," generating an intense media hubbub. He eagarly snorted cocaine, however, for about a year in 1967, he said in a 2004 interview with Uncut magazine. He also tried heroine, which Lennon used regularly in 1969.
Lennon's second wife, Yoko Ono, said in a 2007 BBC Radio interview that a greedy drug dealer who had been cutting their heroin with baby power spared them from worsening dependence. "Luckily we never injected because both of us were totally scared about needles," she recalled.
Many Beatles songs have apparent references to drugs. "I need a fix 'cause I'm going down" they sang in their 1968 hit "Happiness Is a Warm Gun." The psychedelic 1967 anthem "Lucy in the Sky With Diamonds" is said to be about LSD.
But Lucy was a classmate of Lennon's son, band members said, and the song wasn't offering a subliminal message. "My son Julian came in one day with a picture he painted about a school friend of his named Lucy. He had sketched in some stars in the sky and called it 'Lucy in the Sky with Diamonds,' Simple." Lennon said in a 1980 Playboy interview, in which he also said peyote and mushrooms had displaced LSD as his go-to hallucinogens.
That denial was undermined by McCartney, who told Uncut more than two decades later that the song was a "pretty obvious" reference to acid. "A song like 'Got to Get You Into My Life,' that's directly about pot, although everyone missed it at the time," he added. "'Day Tripper,' that's one about acid."