Nicotine, like other addictive substances such as heroin and cocaine, binds to nicotinic choline-like receptors in the central brain nicotine, leading to an increase in the release of dopamine, which in turn brings a sense of calm and pleasure and satisfies psychological needs.
Competitive binding of nicotine to receptors allows for prolonged receptor activation, receptor desensitisation and upregulation; when nicotine levels fall, it causes a state of high receptor stress, leading to drug-seeking behaviour. When smokers quit, the reduced nicotine levels in their blood, combined with psychological and behavioural habits, may result in attempted quitters complaining of discomfort as a result of stopping smoking, such as cravings, irritability, depression, nervousness, irritability, depression, lack of concentration, sleep disturbances and other symptoms, medically known as withdrawal symptoms. The essence of withdrawal symptoms is nicotine dependence and psychological dependence. Withdrawal symptoms occur within a few hours of quitting.
However, withdrawal symptoms are temporary, and are a gradual adjustment of the body’s functions to a non-smoking state. They are most severe in the first week after quitting, and most gradually subside to disappear after three to four weeks.