Final answer:
Tolerance in substance use disorders is when a person needs more of the drug to experience the same effects as before, indicative of physiological dependence.
Step-by-step explanation:
Tolerance in the context of substance use disorder refers to the state whereby an individual requires increasing amounts of a substance to achieve the effects that were previously obtained at lower doses. This phenomenon is a component of physiological dependence and is often observed in individuals diagnosed with substance use disorder. The compulsive pattern of drug use despite facing negative consequences is central to the definition of substance use disorder. Tolerance can be particularly dangerous as it may lead individuals to consume higher doses of the substance, potentially resulting in overdose and death.
In the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), substance use disorder is characterized by both physical and psychological dependence, with criteria including the continued use of drugs despite substantial harm. Tolerance, alongside withdrawal symptoms and drug craving, is an important aspect of diagnosing substance use disorder. While physical dependence leads to withdrawal symptoms upon cessation, psychological dependence involves an emotional need for the drug, often to relieve psychological distress such as anxiety or depression.