Smoking is an addiction in every sense of the word and it is one of the most difficult addictions to beat. So why is smoking addicting? The main reason for this is due the nature of nicotine and the way it interacts with the brain. The emotional dependence and comfort that smoking provides are other reasons why it is so hard to quit smoking.

Nicotine is an extremely addictive poisonous alkaloid that is present in tobacco. When a person smokes, nicotine is immediately absorbed through the lungs into the bloodstream. Within 7 to 10 seconds of inhalation, nicotine crosses the blood-brain barrier and reaches the brain where it triggers a set of complex chemical reactions involving hormones and neurotransmitters. The effects of smoking can then be understood by nicotine’s reaction with three major chemical messengers: dopamine, adrenaline and insulin. These interactions are responsible for the bi-phasic effects of smoking, which paradoxically both invigorates and relaxes the smoker.

Dopamine is the neurotransmitter that activates the reward pathways in our brain and provides the feelings of pleasure and desire that drives addiction. Nicotine has a greater affinity for the receptors that activate dopamine than the body’s own natural dopamine activators. Therefore, it attaches to these receptors and increases the secretion of dopamine which results in the feelings of pleasure, well-being and mild euphoria that is experienced with smoking. However, the direct stimulation of these receptors by nicotine occurs only for a few minutes and although, nicotine also speeds up dopamine release and prevents the body from slowing it down, the effects only lasts for about an hour. The short-lived feelings of pleasure start to fade and the person begins to feel edgy and agitated as they experience the effects of nicotine withdrawal. As the acute effects of nicotine wear off, the smoker continues dosing themselves to obtain relief from the withdrawal symptoms and this relief is the ‘comfort’ and relaxation that smoking provides.

Nicotine also triggers the release of adrenaline also known as the ‘fight or flight’ hormone. Adrenaline increases heart rate and blood pressure leading to rapid, shallow breathing and a racing heartbeat. It also dumps glucose into the blood as a ready source of energy, thus invigorating the smoker. Nicotine inhibits the release of insulin which also results in higher blood glucose. This hyperglycemic (high blood sugar) state signals the body to suppress appetite, which leads to the reduction in hunger often associated with smoking.

These short-term effects alone do not completely explain why smoking is so addictive. The long-term effects of nicotine on the brain lead to an increase in the number of dopamine receptors themselves. This growth and activation of receptors known as ‘up-regulation’ means receptors are de-sensitized and need more and more nicotine to achieve the same high. The vicious cycle is thus completed resulting in an addiction that is hard to beat. These reactions combined with the emotional crutch that smoking provides is responsible for smokers lighting up for every reason: be it for boredom, depression or as a reward.