Los Angeles ? The psychedelic drug psilocybin, the active ingredient in “magic mushrooms,” can improve mood and reduce anxiety and depression in terminal cancer patients, Los Angeles researchers reported Monday.

A single modest dose of the hallucinogen, whose reputation was severely tarnished by widespread nonmedical use in the psychedelic ’60s and ethical lapses by researchers such as Timothy Leary, can improve patients’ functioning for as long as six months, allowing them to spend their last days with more peace, researchers said.

The research was a pilot study involving only 12 patients, but it is viewed as a first step in restoring the drug to respectability.

“This is a landmark study in many ways,” said Dr. Stephen Ross, clinical director of the Center of Excellence on Addiction at New York University’s Langone Medical Center, who was not involved in the research. “This is the first time a paper like this has come out in a prestigious psychiatric journal in 40 years.”

The research conducted on psychedelic drugs in the 1950s and ’60s “was promising, but by no means did it reach the kinds of scientific standards that we would expect today,” said behavioral biologist Roland Griffiths of Johns Hopkins University, who was also not involved in the study.

The new research “is just a pilot study and really needs to be considered preliminary, but it demonstrates that such research can be conducted safely and that doses have palliative effects,” Griffiths said.

Ross and Griffiths have ongoing studies examining the use of psilocybin in cancer patients, but Dr. Charles Grob, a psychiatrist at Harbor-UCLA Medical Center and the Los Angeles Biomedical Research Institute, is the first to report results.

Grob and his colleagues studied 12 patients, ages 36 to 58, with advanced-stage cancer and anxiety resulting from their diagnoses. Each patient went through two sessions, one in which he or she was given the drug and another with a placebo, the drug niacin, which provokes a physiological but not a psychological reaction. Although the doses were blinded, about 80 percent of the time both patients and physicians could tell which drug patients were getting.

Psilocybin is illegal and listed in the same class of drugs as LSD and heroin, according to the Department of Justice.