Nicotine addiction

A couple of weeks ago this column examined a new treatment option for people who want to quit smoking. It is often said that nicotine is the one of the most addictive drugs, and with less than 10% of people in any one year who try to give up actually succeeding, it certainly looks like this is one mighty difficult drug to quit. So why is it so addictive?

Nicotine is a relatively simple substance that easily passes into the bloodstream. From there the drug crosses the important membranes that separate the blood from the brain and can take less than seven seconds to reach the brain from the lungs. Once in the brain, nicotine stimulates certain nerve cells that bring about a state of heightened awareness. Some of the benefits of nicotine that smokers report include an improvement in their reaction time and an increased ability to pay attention. The chemical also stimulates the release, or slows down the breakdown, of the neurotransmitter dopamine, which is part of the body’s reward system. These reward pathways are believed to reinforce behaviours that are good for survival, from eating to sex, making you feel happy and at peace.

The involvement of nicotine in dopamine levels is almost certainly the reason why nicotine is so addictive. A range of other animals, from rats to gorillas, can become addicted to nicotine, indicating that it stimulates this vital reward system. Nicotine may also increase levels of endorphins, natural painkillers, and glutamate, which is part of the memory system. Taken altogether, nicotine stimulates feelings of craving and well-being that are remembered each time a cigarette is smoked or even seen by an addicted smoker.

Unfortunately, like many other drugs, over time the smoker needs greater amounts of nicotine to produce the same levels of euphoria. The chemical affects different parts of the body, particularly the release of adrenaline, which speeds the body up, increasing heart rate, blood pressure and breathing rate. Levels of glucose in the blood can also increase as a result of smoking, raising perceived energy levels. Hence the reason why some smokers say they need a cigarette to wake them up in the morning. Never a good sign!

Recent research also suggests that certain smokers may be predisposed to nicotine addiction through the effects of a gene responsible for metabolising nicotine. Scientists have found that non-smokers are twice as likely to carry a mutation in a gene that helps to rid the body of nicotine. In addition, smokers who carry mutations in the gene, (known as CYP2A6) are likely to smoke less because nicotine is not rapidly removed from the brain and bloodstream. By contrast, smokers with the efficient version of the gene will tend to smoke more heavily to compensate for nicotine being removed more rapidly.

All in all, not particularly good news for smokers!

Remember: If you do not want any negative consequences, do not use the drug and no matter how many times you have used a substance – never be blase!