Final answer:
Stimulants increase alertness and wakefulness, depressants calm the brain and induce sleepiness, and anxiolytics relieve anxiety and can help facilitate sleep. These three classes of drugs impact sleep in different ways.
Step-by-step explanation:
Three classes of drugs that influence sleep are stimulants, depressants, and anxiolytics. Stimulants, such as caffeine and amphetamines, activate the nervous system and can lead to increased wakefulness, making it difficult to fall asleep. In contrast, depressants work by calming the brain and inducing sleepiness; examples include ethanol found in alcoholic beverages and opioids like codeine. Lastly, anxiolytics are drugs that relieve anxiety and often have a tranquilizing effect, which can facilitate sleep. Benzodiazepines such as diazepam (Valium) are common anxiolytics that may be prescribed to aid in sleep.