Nicotine dependence has risen 12 percent from 1989 to 2006, and the percentage of people classed as highly nicotine dependent has risen by 32 percent, US researchers presented the results of a new study at the annual meeting of the American College of Chest Physicians, in Philadelphia.

Nicotine dependence nowadays is the highest it has been in 15 years, according to the study led by Dr. David P. Sachs from the Palo Alto Center for Pulmonary Disease Prevention in California.

Previous studies have shown that the more physically dependent a cigarette smoker is, the more intensive treatment needs to be done in order to cut the patient’s risk for relapse. Almost three-fourths of US smokers are highly physically nicotine dependent, Sachs says, adding that they need much more intensive and individualized treatment to help them quit smoking. Dr. Sachs also noted that “individuals who have less severe nicotine dependence have already been successful at quitting smoking, which leaves a larger percentage of patients who are highly nicotine dependent among the greater tobacco-using community.”

It is estimated that 21 percent of US adults are smokers, including 24 percent of men and 18 percent of women, according to the US Centers for Disease Control and Prevention. The percentage of people who are seen as highly nicotine dependent is extremely high, but the reasons for the increase in nicotine addiction are unknown.

Quit-smoking programs should also target those 10% of smokers that are actually not nicotine-dependent.

Also, a lot of smokers are genetically dependent to nicotine. These persons are much more likely to go on to become regular smokers because they have a gene type implicated in the development of lung cancer that increases their addiction risk. One of the reasons for the decline in smoking cessation rates might be the increasing difficulty in achieving this goal because of the high degree of dependence.