New research out of the Palo Alto Center for Pulmonary Disease Prevention shows that nicotine dependence in the U.S. is at its highest level since 1993, with 75 percent of those seeking tobacco-dependence treatment considered highly dependent on nicotine.

Researchers studied pretreatment nicotine dependence severity in 630 subjects between 1989-2006 and found that participants' pretreatment addiction scores increased by 12 percent over the last 15 years. The study authors could not pinpoint a definite cause for the trend; however, "Previous studies suggest 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," said lead author David Sachs.

The study's findings highlight the need for more individualized tobacco-dependent treatments and possible increases in pharmacologic doses and duration of medical use, the researchers said. "Today's severely nicotine-dependent patient may not respond to the current 'standard' in tobacco dependence treatment, much of which is based on nicotine dependence data and outmoded treatment concepts from 15 years ago," Sachs said.

The study's results were presented at the 74th annual international scientific assembly of the American College of Chest Physicians.