Oct. 27, 2004 -- Just like heroin and morphine, smoking cigarettes triggers the
release of addictive "feel-good" brain chemicals, new research shows.
The finding helps researchers understand why smokers have such a tough time
quitting despite all the health dangers. They presented their report at the
annual meeting of the Society for Neuroscience, held this week in San
It's the first human study to show that smoking cigarettes stimulates the
brain's production of chemicals called opioids. The opioids are known
to play a role in soothing pain, increasing positive emotions, and creating a
sense of reward. Both morphine and heroin trigger this same chemical flow.
The new study also confirms previous findings -- from animal studies -- that
smoking cigarettes affects the flow of another feel-good brain chemical called
dopamine. Researchers are now investigating the interaction between the two
chemicals in the brains of smokers and nonsmokers.
"It appears that smokers have an altered opioid flow all the time, when
compared with non-smokers, and that smoking a cigarette further alters that
flow by 20 to 30 percent in regions of the brain important to emotions and
craving," says lead researcher David J. Scott, a graduate student in
neuroscience at the University of Michigan in Ann Arbor, in a news release.
Scott's research team spent several years testing a way of using PET imaging
(positive emission tomography) to study the opioid system in the brain. The
scans don't show the flow of opioids directly, but they do show opioid receptor
activity in the brain.
Morphine and heroin are among the drugs that bind to these receptors.
The University of Michigan researchers have also created a system that
allows someone to smoke cigarettes while lying in the PET scanner having his or
her brain scanned.
That's how they conducted this new study, which involved six healthy men who
smoked one pack per day. All refrained from smoking cigarettes for at least 10
hours before the study began. During their brain scans, each first smoked a
cigarette almost devoid of nicotine, and then smoked a regular cigarette.