Withdrawal symptoms refer to physical and emotional signs that occur when a person who has been using a substance or medication suddenly stops or reduces their use. These symptoms can vary depending on the type of substance being used, but common withdrawal symptoms include anxiety, irritability, depression, fatigue, headaches, sweating, tremors and in some cases seizures or even death if the withdrawal is severe enough. Withdrawal symptoms occur because the body has become dependent on the substance to function normally, so when it's removed or reduced, the body struggles to adjust.