What type of substances are sedative-hypnotics?

Sedative-hypnotics are characterized as substances that induce depression on the central nervous system (CNS). These substances are primarily utilized to promote relaxation, reduce anxiety, and facilitate sleep. Their mechanism of action involves enhancing the effects of neurotransmitters such as GABA, which leads to a calming effect on the brain and body. This is why sedative-hypnotics are commonly prescribed for conditions like insomnia and anxiety disorders.

In contrast, the other options describe different categories of substances. Stimulants, for instance, are known to elevate CNS activity, while vitamins do not function as sedative-hypnotics and instead might be involved in cognitive enhancement. Additionally, therapeutic agents that stimulate appetite specifically target a different physiological response and are unrelated to the depressant effects of sedative-hypnotics. Thus, option B accurately captures the defining characteristic of sedative-hypnotics.