Final answer:
The stimulant that requires individuals to be at least 18 years old to legally use is nicotine. It is regulated by the FDA and is known for its addictive properties in tobacco products. Cannabis is also regulated, with varying laws by state and typically a higher age requirement.
Step-by-step explanation:
The psychoactive stimulant that requires an individual to be at least 18 years old to legally use is nicotine. In the United States, nicotine is a legal substance known for its addictive qualities, and it is the active ingredient found in cigarettes and other tobacco products. The Food and Drug Administration (FDA) regulates its sale and distribution, imposing age restrictions to prevent underage smoking.
Besides nicotine, cannabis (marijuana) is another substance with varying legal statuses. It is regulated federally as a Schedule 1 drug but is legal for medicinal or recreational use in certain states, though purchase and consumption laws typically require users to be 21 years of age or older. Regulation of these substances poses complex legal challenges due to discrepancies between federal and state laws, especially concerning cannabis.