How much a cigarette affects someone at different times of the day — and how hard it is to quit smoking — may depend on individual brain chemistry, according to scientists at the University of Colorado.
Researchers led by Jerry Stitzel, an assistant professor in CU's department of integrative physiology, studied the effects of nicotine on mice and found that there may be real biochemical reasons why some people say their first cigarette of the day is the most satisfying and that smoking seems to lose its buzz at night.
The research, which Stitzel presented at an annual neuroscience conference Monday, studied mice that recognized melatonin — a hormone triggered by darkness and thought to tell our bodieswhen to sleep — and mice that didn't. Melatonin-sensitive mice experienced the addictive effects of nicotine less intensely when the hormone was present.
Melatonin has also been used in other studies to help reduce jet lag, treat sleep disorders and establish circadian rhythms in the blind, according to the Mayo Clinic.
The effects of nicotine on the mice were greatest when levels of the stress hormone corticosterone were high, which typically happens first thing in the morning. People experience the same phenomenon with cortisol, the human equivalent to corticosterone.
"The negative health consequences of smoking have become well known, and a large majority of smokers say that they would like to quit," Stitzel said in a news release. "As such, we need to understand the interaction between smoking, genes and internal chemistry so we can target new therapies to those who have a hard time quitting."
Nationwide, nearly 60 percent of regular smokers attempted to quit smoking in 2006, according to the Center for Disease Control.
Smoking causes about 438,000 deaths and results in an estimated $167 billion in health-care costs a year, plus lost productivity, the center said.
In Colorado, 18 percent of adults ages 18 to 35 smoke. The rate is 29 percent in Kentucky, the highest in the country, and 10 percent in Utah, the lowest.