One of the reasons smokers find quitting so challenging is the highly addictive nicotine that is found in cigarettes. Over time, smokers become both physically and emotionally dependent on their habit. During inhalation, nicotine quickly enters the bloodstream, reaching the brain in a matter of seconds.

Once in the brain, it interacts with specific receptors to trigger feelings of pleasure. The body adapts to the nicotine and the smoker develops a tolerance, meaning that they have to smoke more to get the feelings they desire. When they try to cut back or quit, the body craves nicotine, leading to withdrawal symptoms.

Withdrawal symptoms can start within a few hours of the last cigarette, but tend to peak two to three days later. Symptoms may persist for anything from a few days to several weeks and can include headache, irritability, restlessness, reduced concentration and insomnia. Quitters may also experience depression, anxiety, dizziness and increased appetite.

Psychological symptoms may also occur as smokers associate certain situations with having a cigarette, which results in temptation. These so-called €situational cravings€ can greatly challenge a person's willpower.