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ลำดับตอนที่ #5 : How nicotine works

         Nicotine causes chemical or biological changes in the brain. This effect is called psychoactive and although it is less dramatic than heroin or cocaine, the strength of the addiction is just as powerful. It is a 'reinforcing' drug, which means that users desire the drug regardless of the damaging effects. For example, in research conducted in 1994, only 50% of smokers who suffered a heart attack managed to quit smoking even though their doctors advised them to. Coincidentally, 50% of all regular smokers die as a result of smoking. 

Nicotine addiction is a physical dependency. Withdrawal symptoms are severe and most smokers cannot quit on their first attempt because of these symptoms. 

The human body builds a tolerance to nicotine and the effect of the drug is reduced over time. As a result, regular smokers can inhale greater amounts of smoke and therefore greater amounts of toxins, without showing immediate effects (such as coughing, nausea). 

Nicotine is extremely poisonous if consumed in large amounts and most people feel sick and dizzy the first time they smoke. These negative affects are quickly overcome. Over time the body builds a tolerance to nicotine, resulting in an increase in the amount of cigarettes smoked.