Nicotine may improve the symptoms of depression in people who do not smoke, Duke University Medical Center scientists reported.

The researchers emphasized that the hazards of tobacco mean that people should not take up smoking or buy nicotine patches to fight depression.

They said in a news release that it may be possible to safely manipulate nicotine to reap the benefits without the addictive properties.

"Our study also provides evidence that smokers may indeed smoke, in part, to improve their mood -- a notion that has been quite controversial in the field," said lead investigator Joseph McClernon.

The work was meant to explore theories about higher smoking rates among people with depression.

"People with depression may be self-medicating by smoking, albeit in a deadly way," said Edward Levin, a psychiatry professor involved in the study.

The research looked at 11 people who did not smoke. They were given either a nicotine patch or a placebo.

Participants who wore the nicotine patch for at least eight days experienced a significant decline in their depression-assessment rating scores.

Nicotine stimulates the release of specific neurotransmitters, including serotonin, dopamine, and norepinephrine, which carry messages between nerve cells. Depression has been linked to chemical imbalances of these neurotransmitters, McClernon said.

The study also suggests that people prone to depression may need extra help in order to quit smoking, such as nicotine replacement therapy, the scientists said.