Psychology MCAT Practice Exam 2026 – Complete All-in-One Guide to Ensure Your Success!

Tolerance in the context of substance-related disorders is best defined as a decrease in sensitivity to a drug, which is typically characterized by the need to consume larger amounts of the substance to achieve the same psychoactive effects. This physiological adaptation occurs because the body becomes accustomed to the presence of the drug, leading to changes in its neurotransmitter systems and metabolic processes. As tolerance builds, individuals may find that their previous doses no longer provide the desired effects, prompting them to increase their intake.

The other options address different phenomena related to substance use disorders. A decrease in withdrawal symptoms relates more closely to the withdrawal phase rather than tolerance itself. The strong desire to ingest a drug is indicative of cravings, which are separate from the concept of tolerance. Lastly, an increase in cravings indicates a psychological relationship with the substance but also does not directly define tolerance, which is fundamentally about the body's diminished response to the drug's effects over time.