Smoking addiction comes from nicotine, originally found in tobacco products and now prevalent in tobacco-free flavored vape pens, gums, and other consumables. Nicotine consumption creates a dopamine cycle in the brain, which teaches the brain to crave the cycle of behavior repeatedly. Even a few weeks of regular nicotine use leads to addiction. Nicotine affects all areas of your body, from your heart and blood vessels to your hormones, metabolism, and brain. When quitting smoking, a user may go through withdrawal for up to a month. Common withdrawal symptoms include headaches, anxiety, depression, irritability, cough, cravings, insomnia, fatigue, constipation and mental fog. In addition to cigarettes, some marijuana smokers also report experiencing addiction, although with different characteristics.