Information on how to get adolescent smokers to quit is severely lacking, according to a new research review from experts in the U.K.

The Health Behavior News Service reported Nov. 20 that the authors noted that most research on teen smoking has focused on prevention, not treatment, even though a third of smokers start by age 14, and 90 percent are smoking by age 21.

"There is not yet sufficient evidence to test the effectiveness of smoking-cessation programs for adolescents, although some approaches show promise," noted review authors led by Gill Grimshaw of the University of Warwick.

Experts say cessation programs need to be tailored to the needs of adolescents, whose addictions may differ from adults' and for whom genetic factors may play a key role, possibly limiting the effectiveness of nicotine-replacement therapy.

The review covered 15 research reports; two included giving nicotine-replacement therapy to teens, to little effect; nine used motivational therapy to encourage teens to quit, but had mixed results. Others tried to get teens to quit smoking for short periods of time.

The review appears in the latest issue of The Cochrane Library.