Each year, smoking causes more than 440,000 premature deaths in the United States, making smoking the leading cause of preventable death, according to the Duke Center for Nicotine and Smoking Cessation Research. Despite this fact, millions of Americans continue to smoke. Approximately 35 million Americans say they want to quit smoking, but roughly 85 percent of people who try to quit smoking relapse within one week, the National Institute on Drug Abuse reports. These people cannot quit because they are addicted to smoking. Smoking addiction has one primary cause: nicotine.
Nicotine Addiction
Nicotine is a highly addictive chemical found in tobacco smoke. Addiction is defined as compulsive drug seeking despite the known negative health consequences. The reason nicotine is so addictive is that is activates the brain's reward centers. Nicotine acts like a neurotransmitter in the brain called acetylcholine, the National Institute on Drug Abuse for Teens explains. Mimicking the action of acetylcholine, nicotine binds to receptors in the brain called cholinergic receptors, which trigger the release of another neurotransmitter called dopamine. Dopamine is the pleasure molecule of the brain; it is released during any pleasurable experience. When nicotine reaches the brain, it causes the release of excess dopamine, which causes a pleasurable sensation.
Nicotine Tolerance
The pleasurable sensation caused by nicotine peaks about 10 seconds after inhalation, explains the National Institute on Drug Abuse. That means the pleasurable sensation caused by smoking disappears rapidly, causing people to want to repeat the pleasurable sensation and smoke again. In addition, exposure to nicotine causes the cholinergic receptors to become less sensitive to nicotine, meaning that a larger dose of nicotine must be consumed in order to feel the same amount of pleasure. This cycle is responsible for the escalating nature of smoking addiction.
Nicotine Withdrawal
A smoker can start to feel symptoms of nicotine withdrawal within two to three hours after the last use of tobacco, MedlinePlus reports. The symptoms often peak two to three days later and may subside a little after that. However, some long-term smokers may experience symptoms for up to six months or more. The symptoms of nicotine withdrawal include severe irritability, anxiety, frustration and restlessness. One of the worst symptoms reported is an intense craving for nicotine, which is often the main reason for a relapse. Nicotine withdrawal may also cause difficulty concentrating and falling asleep, and may cause bad dreams or nightmares. Headaches, increased appetite and weight gain are additional symptoms.
Behavioral Patterns
In addition to the physiological addiction to nicotine, behavioral conditioning also plays a role in smoking addiction. For some smokers, the smell, sight or feel of a cigarette may spark intense cravings. Additionally, the ritual of holding, lighting and smoking a cigarette may also be conditioned as part of the pleasurable experience of smoking. These behavioral factors may be the reason why nicotine replacement therapies, such as nicotine gum or patches, do not completely stop cigarette cravings.
