It is difficult to quit smoking because the nicotine in tobacco smoke is so addictive. Nicotine impacts the central nervous system, causing a release of epinephrine, a hormone that causes a “rush” of energy. After this stimulus subsides, a sedative effect takes over. This rapidly progresses to withdrawal symptoms that compel the smoker to reach for another cigarette.

One particularly ominous aspect of a smoking (or most any drug) habit is that the user becomes sensitized to the addictive component of the substance – in this case, nicotine. Consequently, the number of cigarettes needed to retain that same metabolic “rush” is increased, leading smokers to steadily increase their intake of cigarettes. Naturally, this also complicates withdrawal from nicotine.

The higher the circulating levels of nicotine, the more difficult it is to quit and the more severe the withdrawal symptoms, including:

• Irritability
• Cravings
• Difficulty concentrating or paying attention
• Trouble sleeping
• Increased appetite (although some experts believe people eat more after quitting smoking because food is regaining full flavor for them)

These withdrawal symptoms may begin within a few hours of the last cigarette and generally grow more severe, peaking after a few days and subsiding in a few weeks.

Not all tobacco users are addicted to nicotine. Nicotine dependence is marked by the following:

• Serious, yet unsuccessful attempts to stop tobacco use.
  
  
• Physical withdrawal symptoms during periods of quitting smoking.
  
  
• Continued tobacco use despite a serious physical problem that the user knows is made worse through continued tobacco use, such as cardiovascular disease, respiratory illness or cancer.
  
  
• User has developed a tolerance for nicotine created by the accumulation of nicotine in the body. Each additional intake produces less of an effect, causing the user to increase the frequency and or amount of nicotine intake.

Nicotine is also psychologically addictive. It delays the breakdown of the nerve impulse that influences alertness, pain reduction, learning and memory (acetylcholine). As a result, nicotine stimulates memory and alertness, and improves mental speed and reaction time. Nicotine may also alter the user’s mood by stimulating the production of the brain’s “pleasure” chemicals, including dopamine, beta-endorphin, epinephrine, norepinephrine, arginine and vasopressin. Nicotine reduces stress and the body’s aggressive response to stressful situations. Furthermore, nicotine suppresses the appetite, especially for sweets (simple carbohydrates). For some users, the ritual act of smoking itself (e.g., the holding and lighting of the cigarette) is part of the pleasure.

Because of this emotional as well as physical addiction, people may continue to experience cravings for nicotine even months after they have quit smoking. In other words, they may still crave nicotine for emotional reasons even after nicotine is no longer affecting their body physically. Ex-smokers who are tempted to “give in” and begin smoking again are strongly encouraged to speak with a trusted friend, family member or health care professional.