What Causes Nicotine Addiction?

By itself, nicotine is thought to have benefits as a medicine. It has been shown to improve attention and cognitive performance, and nicotine enemas are an effective treatment for ulcerative colitis.

When nicotine is smoked, however, it is a different story. When smoked, nicotine is absorbed by the lungs and quickly moved into the bloodstream, where it is circulated throughout the brain. Nicotine reaches the brain within eight seconds of a person inhaling tobacco smoke.

As with any drug, nicotine’s potential to be addictive is related to how fast it reaches the brain. Smoking and injecting any mood-altering substance dramatically increases a drug’s addiction potential because it reaches the brain faster.

Consider cocaine, for example: For years, experts did not believe that snorting cocaine was addictive. Then came the invention of crack—the same drug, but in a different form and with faster delivery to the brain because it is smoked or injected.

So while people don’t abuse nicotine replacement products in the form of patches and gum, when smoked, it is addictive.

How nicotine produces its pleasurable effects and why it’s so addictive has been the focus of much research over the past 20 years. Nicotine and other ingredients in cigarette smoke act upon structures deep in the brain, where emotions and survival drives are located. When stimulated, these structures produce a feeling of pleasure.

Specifically, nicotine stimulates the release of a neurotransmitter (a chemical messenger) called dopamine (sometimes referred to as the pleasure molecule) in an area of the brain called the nucleus accumbens, which is an important part of the brain’s reward system, where feelings of pleasure and reward are produced. This part of the brain is the primary target of most drugs of abuse.

The human brain is not prepared for the effects of nicotine and misinterprets the experience of smoking as something especially significant or profound. It’s difficult for the brain to ignore inhaled nicotine.

The brain tells a smoker that smoking is good—just as it tells you that food is good when you’re hungry. Because of these effects on the brain, the urge to smoke often overrides rational thought and good judgment. Consequently, many addicted smokers find themselves standing outside in very hot or cold weather, sneaking a smoke in the stairwell, all the while knowing they are inhaling a substance they know will harm them. And because tolerance to nicotine develops rapidly, higher doses and more frequent use are required for the brain to register the same level of pleasure experienced during initial use.

By Drew Edwards, MS; Mark S. Gold, MD
© 1999 University of Florida McKnight Brain Institute