You initially become addicted to cigarettes because of the fast action of nicotine on the pleasure centers of your brain. When you puff on a cigarette, the nicotine in your lungs enters your blood stream and within 15 to 20 seconds begins to work on your brain.
Once in your brain, nicotine binds to receptors that are intended for the neurotransmitter acetylcholine. This binding causes a change in the cell walls that allow calcium or sodium ions to enter the cell. After that, a number of additional brain neurotransmitters are released.
These neurotransmitters affect your mood and behavior. The neurotransmitter dopamine affects the reward center that causes feelings of pleasure and enjoyment. Serotonin helps moderate your mood and controls your appetite. GABA produces a calming effect that reduces anxiety.
Smoking is a means of artificially spiking the acetylcholine system resulting in feelings of pleasure, calmness, and a moderation of your mood. Because of these positive effects and the speed with which they are associated with nicotine intake (taking a puff) smoking is highly addictive.
As an occasional or social smoker, you may begin to use cigarettes as a means of coping with life's daily stresses. You switch from social smoking to daily smoking. Once you begin smoking several cigarettes a day, nicotine is constantly stimulating your brain, 24 hours a day. You are psychologically addicted to the positive effects of nicotine.
Over a period of several years a transition begins to take place in the addiction mechanism.
Your brain adapts to the frequent presence of nicotine. Your brain physically changes by increasing the nicotine receptor concentration. This requires more nicotine for your brain to function properly. That is, your brain now becomes dependent on nicotine for normal functions. This adaptation produces tolerance for nicotine.
When your brain is unable to get the required amount of nicotine, you experience withdrawal symptoms. These withdrawal symptoms include irritability, restlessness, difficulty in getting along with family and friends, sleeplessness, anxiety, depression, hunger, difficulty concentrating, and lethargy.
Half the nicotine in your body is metabolized and broken down every 2 hours. As your nicotine level declines, the withdrawal symptoms set in. The only way to relieve the withdrawal symptoms is with another dose of nicotine. You now smoke, not for pleasure, but to eliminate withdrawal symptoms.
As an addicted cigarette smoker, you often need your first dose of nicotine as soon as possible in the morning. Many smokers take their first puffs within 5 minutes of awakening.
Throughout the day, you need additional doses of nicotine every couple of hours. You are often willing to leave the comfort of a smoke-free environment to stand in the freezing cold, rain, or sweltering heat to get your next dose of nicotine. You are definitely in the second stage of nicotine addiction.
Overall, your smoking addiction started out as a psychologically addiction to the positive effects of nicotine on your brain. But, because the brain adapts to nicotine, your smoking addiction winds up as a means of preventing the negative effects of withdrawal symptoms.