CHICAGO - Can laughing gas help smokers kick the habit? Scientists have a whiff of evidence that it might.
When seven smokers went through a single session of breathing nitrous oxide, five quit for at least three days. Four were still tobacco-free when checked a month later.
How does it work? ''That's the million-dollar question,'' said psychiatrist Dr. Carlo Bayrakdarian of the Weill Cornell Medical College of New York Presbyterian Hospital.
Laughing gas would be just a first step in treatment, to get over the initial ''hump'' of craving before a person moves on to a longer-term strategy to stay off tobacco, he said.
Bayrakdarian said he did the study after reading about a South African researcher who was using the gas to prevent alcohol withdrawal. He reported the results of his preliminary study Wednesday at a meeting of the American Psychiatric Association.
Dr. Richard Hurt, director of the nicotine dependence center at the Mayo Clinic, called the result interesting. But he stressed the idea must be tested in more people, with the gas pitted against a placebo.
Bayrakdarian said he hopes to do such a study. His initial work received no outside funding, he said.
On the day of treatment, participants avoided smoking beforehand so they could feel their nicotine craving. Then they breathed nitrous oxide and oxygen for a maximum of 20 minutes, or just until their craving was gone.
For the next three days they kept a diary of their smoking. They then returned to give a urine sample that was tested to reveal whether they had lit up.
All seven smokers smoked fewer cigarettes in the three days after treatment, with an overall decrease of 81 percent, Bayrakdarian said.