Psychoactive drugs impact brain function, influencing perception, mood, consciousness, cognition, and behavior. These substances are grouped based on their effects and the mechanisms by which they act.

Stimulants such as cocaine, amphetamines, and nicotine enhance brain activity, leading to increased alertness, attention, and energy. These drugs typically raise heart rate, blood pressure, and body temperature. While they can induce feelings of euphoria, their misuse can result in severe health issues, including addiction, heart problems, and psychological disorders.

Depressants, which include alcohol, barbiturates, and benzodiazepines, slow brain activity to produce relaxation. These can diminish anxiety and inhibitions but may dangerously lower heart rate and blood pressure and impair cognitive functions at higher doses.

Opiates, primarily used for pain relief, include substances like morphine and heroin. They generally produce euphoria and a profound sense of well-being but carry risks such as addiction, respiratory depression, and death from overdose.

Hallucinogens like LSD, MDMA, and psilocybin bring about significant changes in perception, mood, and thought. The effects of these substances can vary greatly depending on the drug, dosage, and individual, often leading to altered sensory experiences and emotional shifts.

Additionally, some drugs like cannabis do not fit neatly into these categories, displaying properties of stimulants, depressants, and hallucinogens based on their chemical makeup and the user's biological response.

Overall, psychoactive drugs interact with neurotransmitter systems in the brain. Their effects can range from therapeutic to recreational to harmful, depending largely on usage patterns and individual susceptibility. Understanding these drug categories is crucial for medical use, potential therapies, and recognizing the risks associated with their abuse.