Smoking tobacco is an addiction and a serious health hazard for the consumer. It is important to understand that all forms of tobacco are toxic: the presence of nicotine from the alkaloid family creates addictive effects and has chronic long-term toxicity. People who smoke gradually develop physical, psychological and behavioural dependence, with signs of withdrawal such as anxiety, irritability, sleep disturbance, concentration disorders and even depression. Addiction, internet addiction, gambling, sex, alcohol, drugs and food are treated separately.