Final answer:
Depressants are drugs that lower anxiety and inhibitions by suppressing central nervous system activity, making them effective for treating anxiety and insomnia.
Step-by-step explanation:
Drugs that are often used because they lower anxiety and inhibitions are primarily depressants. Depressants are substances that suppress central nervous system activity. They can serve as agonists of the gamma-Aminobutyric acid (GABA) neurotransmitter system, which has a quieting effect on the brain. This makes depressants effective for treating conditions like anxiety and insomnia. Examples of depressants include barbiturates, benzodiazepines, and opioids such as codeine and heroin.