Because California does not require doctors to report cases involving medical marijuana, no reliable data exist for how many minors have been authorized to receive it. But Dr. Jean Talleyrand, who founded MediCann, a network in Oakland of 20 clinics who authorize patients to use the drug, said his staff members had treated as many as 50 patients ages 14 to 18 who had A.D.H.D. Bay Area doctors have been at the forefront of the fierce debate about medical marijuana, winning tolerance for people with grave illnesses like terminal cancer and AIDS. Yet as these doctors use their discretion more liberally, such support  even here  may be harder to muster, especially when it comes to using marijuana to treat adolescents with A.D.H.D.

“How many ways can one say ‘one of the worst ideas of all time?’ ” asked Stephen Hinshaw, the chairman of the psychology department at the University of California, Berkeley. He cited studies showing that tetrahydrocannabinol, or THC, the active ingredient in cannabis, disrupts attention, memory and concentration  functions already compromised in people with the attention-deficit disorder.

Advocates are just as adamant, though they are in a distinct minority. “It’s safer than aspirin,” Dr. Talleyrand said. He and other marijuana advocates maintain that it is also safer than methylphenidate (Ritalin), the stimulant prescription drug most often used to treat A.D.H.D. That drug has documented potential side effects including insomnia, depression, facial tics and stunted growth.

In 1996, voters approved a ballot proposition making California the first state to legalize medical marijuana. Twelve other states have followed suit  allowing cannabis for several specified, serious conditions including cancer and AIDS  but only California adds the grab-bag phrase “for any other illness for which marijuana provides relief.”

Image Patients line up as marijuana is dispensed for medical use at Wo/Men’s Alliance for Medical Marijuana, a collective in Santa Cruz. Credit... Monica Almeida/The New York Times

This has left those doctors willing to “recommend” cannabis  in the Alice-in-Wonderland world of medical marijuana, they cannot legally prescribe it  with leeway that some use to a daring degree. “You can get it for a backache,” said Keith Stroup, the founder of the National Organization for the Reform of Marijuana Laws.