May 7, 1999

Bucking the conventional wisdom, a French scientist has suggested that the world's favorite morning pick-me-up-caffeine-is not addictive.

Millions of people worldwide start their day with a cup of caffeine-containing coffee or tea, and many report withdrawal effects, particularly headache and achiness, if they abruptly cease their morning libation. But according to Astrid Nehlig, Ph.D., research director at the National Health and Medical Research Institute in Strasbourg, France, a study using laboratory animals found that drinking the equivalent of one to three cups of coffee daily enhanced alertness without creating withdrawal symptoms when the animals' caffeine intake was cut off.

The findings fly in the face of both earlier research and decades of anecdotal observation, but Nehlig is undeterred. The difference, she contends, is that caffeine, unlike addictive drugs such as nicotine, heroin, and cocaine, does not trigger activity in the brain's nucleus accumbens in the doses usually consumed by humans. Only in doses equal to about three to eight cups of caffeinated coffee consumed in rapid succession is that part of the brain activated.

"Activation of the circuitry of addiction and reward occurs only at high doses of caffeine, which [in most cases] induce adverse effects," said Nehlig.

She presented her findings at the March meeting of the American Chemical Society in Anaheim, Calif., and has submitted her work for publication to the British journal Neuropharmacology.

What about those headaches, Psychiatric News asked Nehlig? It is clear that "caffeine withdrawal can induce symptoms such as headaches," she replied. But that is only one of seven criteria specified in DSM-IV and ICD-10 that define "true dependence," she asserted. Caffeine is consumed mainly to regulate mood and performance, and "possibly to alleviate some of the overnight symptoms of withdrawal," Nehlig said.

Other psychopharmacologists have not fully swallowed Nehlig's hypothesis.

George Koob, Ph.D., is a professor of neuropharmacology at the Scripps Research Institute in La Jolla, Calif. Caffeine consumption can "meet the criteria for substance dependence" but not to the same degree as with other drugs, said Koob. "You don't see the compulsive use and loss of control you see with" drugs such as cocaine, amphetamine, and alcohol, he said. "But there clearly is a withdrawal syndrome even with two to three cup a day dosing."

Nonetheless, there is "definitely something different about caffeine," Koob added. "I think it is less addicting because the tolerance is so complete." In some cases tolerance drives addictive behavior, while in other cases, including with caffeine and the hallucinogen LSD, tolerance is so complete that it discourages a chronic destructive pattern of abuse, said Koob.

Marc Galanter, M.D., a consultant to APA's Council on Addiction Psychiatry, is a professor of psychiatry and director of the division of alcoholism and drug abuse at the New York University School of Medicine in Manhattan.

A study published in the Lancet a number of years ago clarified "the addictive nature-and I use the term colloquially-of coffee use," Galanter noted. In that study decaffeinated coffee was mixed with caffeinated coffee in the coffee pots located in the dayroom of a mental hospital, he explained. Investigators found that people using the coffee pot with the decaffeinated mix "increased their consumption up to the point where they would consume as much caffeine as they had consumed previously with fully caffeinated coffee," he said.

It is true, however, that chronic caffeine consumption would not meet many of the DSM-IV criteria for dependence, Galanter said. However, "there is no question that it produces a withdrawal syndrome, that seeking coffee shapes behavior among people who drink a fair amount, and that it does cause development of a certain level of tolerance."

Although caffeine does appear "to some extent addictive to a small subset of the population, it is very different from the dependence on hard drugs and is regulated by different mechanisms," Nehlig said. "The risk of intoxication and morbidity with caffeine is almost negligible, which is not the case" for cocaine, nicotine, and other abusable drugs, she added. This difference "may be related to the difference in the effects of caffeine and hard drugs on the nucleus accumbens."

Nehlig conceded that her research would not close the debate over caffeine's addictive potential. Scientists will surely continue to debate the topic over fragrant, steaming cups of coffee that are ubiquitous during breaks at major scientific meetings worldwide.-R.B.K.