The three categories drugs may be organized into are depressants, stimulants, and hallucinogens. As a result, "suppressants" and "barbiturates" would be incorrect options. Opiates (i.e. opium, morphine, and heroin) may be considered depressants because they depress neural functions. As the nervous system is slowed, the individual may feel a sense of pleasure. In the meantime, pupils will constrict and breathing will slow down. These are not the effects of stimulants and hallucinogens; therefore, those options would be incorrect as well.

Stimulants are chemicals known to stimulate the nervous system. It will excite neural activity and body functions. Physiological effects include dilated pupils, increased blood pressure, an increase in blood sugar, and a resulting decrease in appetite that coincide with increased energy levels. LSD would not be considered a stimulant because it is a hallucinogen. This means that it will distort perception and create sensory images without the sensory stimulus.

Cocaine is considered to be a stimulant because it is known to excite neural processes and body functions. These effects have been observed in other stimulants such as caffeine and nicotine. Cocaine users will receive an immediate sense of euphoria because of the drug's ability to interfere with and deplete the brain's source of dopamine, serotonin and norepinephrine. Within hours a crash will set in, this leaves the individual depressed and agitated.

To some degree, most individuals are open for suggestions; however, there are some that are more open to them than others. These individuals are more likely to be hypnotizable. For instance, this may be observed in the phenomenon known as postural sway. In this process, a group of individuals are lined up and told to stand straight with their eyes closed. Afterwards, a person will randomly call out individuals and tell them that they are swaying. It has been observed that people who are highly open to suggestion may begin to sway when they were not previously. These types of individuals are more likely to experience hypnosis.

Tolerance is what occurs when the effects of the same dose of drug diminishes over extended use. Upon repeated exposure, the brain will begin to adjust its chemistry to counteract the effects of the drug. Because exposure needs to be regular for tolerance to occur, the option about random exposure would be incorrect. It's common to observe those who have become tolerant to begin increasing their usual dose. This is a potential outcome of tolerance; therefore, this option is incorrect. While some drugs may have an affect on individuals upon exposure only once, this does not entail tolerance. This becomes a matter of an individual becoming "hooked" on the drug; therefore, this option would also be incorrect. When an individual decides to stop, the body may undergo withdrawal if the individual has developed a physical dependence and is addicted to the drug; thus, this answer is also incorrect.

Alpha waves are a type of brain wave that occurs when a person is about to fall asleep. The person will be relaxed and unfocused but still aware of their surroundings.

Alcohol, prescription painkillers, tranquilizers, heroin, and others affect the nervous system in a depressive manner. This class of drugs generally lowers neurotransmitter levels and decreases central nervous system functions.

Amphetamine is an excitatory drug that affects the neurotransmitter norepinephrine. Alcohol and morphine are depressants, whereas LSD and psilocybin are hallucinogens.

Cocaine is excitatory and stimulates the release of neurotransmitters such as dopamine, serotonin, and norepinephrine.

Throughout human history, people have utilized naturally occurring substances to reach altered states of consciousness. These substances range widely among the categorizations that modern Western science has created, including stimulants (e.g. coffee), depressants (e.g. wine), and hallucinogens (e.g. certain mushrooms). Generally, drug addiction and abuse has only become a problem with the advent and manipulation of synthetic drugs, along with social changes and stresses.