Withdrawal syndrome is a set of physical and psychological symptoms that occur when a person suddenly stops using a substance they are dependent on. It can manifest as physical symptoms such as nausea, vomiting, and headaches, as well as psychological symptoms such as anxiety and depression. As the syndrome progresses, the intensity of the symptoms can increase, leading to difficulty sleeping, increased irritability, and increased cravings for the substance. In some cases, withdrawal can also lead to seizures or delirium.