Final answer:
Withdrawal symptoms are mainly due to decreased stimulation of dopamine receptors following the body's adjustment to a drug's effects. Physical dependence and tolerance are significant factors in substance use disorder and can lead to severe withdrawal symptoms requiring medical supervision.
Step-by-step explanation:
When drug abusers suddenly stop using drugs, the main reason for withdrawal symptoms is c. decreased stimulation of certain dopamine receptors as the result of the body's compensation for the over-activity the drug caused. Drug withdrawal usually involves a variety of negative symptoms that are the opposite of the drug's effects, occurring because the individual's body has adapted to the presence of the drug. For instance, if the drug was producing excessive dopamine activity, the body might have decreased its own dopamine production or receptor sensitivity. When the drug is no longer present, there's less dopamine activity than normal, leading to withdrawal symptoms.
Physical dependence along with psychological dependence plays a significant role in substance use disorder defined in DSM-5. The concept of tolerance is crucial as well, where more of the drug is required to achieve the effects once experienced at lower doses, potentially leading to dangerous levels of consumption. Withdrawal symptoms can be life-threatening in cases of long-term abuse of substances like alcohol and barbiturates, therefore, medical supervision is recommended during detoxification.