drugs that affect the brain by increasing ________ activity are the most commonly misused ones.

Drugs that affect the brain by increasing stimulant activity are the most commonly misused ones. Stimulant drugs increase brain activity by enhancing the effects of neurotransmitters like dopamine and norepinephrine, leading to increased alertness, energy, and feelings of euphoria. Commonly misused stimulants include amphetamines, cocaine, and methamphetamine. These drugs cause neurons to release abnormally large amounts of neurotransmitters or prevent their normal recycling, disrupting normal brain communication and contributing to their addictive potential. Misuse of these stimulants can lead to significant health risks, including addiction, cognitive impairments, and psychiatric conditions such as psychosis and paranoia.