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.

Stimulants like cocaine and amphetamines primarily raise the physiological arousal of the body and boost mood resulting in elation, excitement, increased energy and focus, and reduced fatigue. Other drugs, such as barbiturates, alcohol, and hallucinogens have different effects.

Tolerance is a diminished response to a drug. It can involve less of an effect with the same amount of a drug, or needing more of a drug to have the same effect. Withdrawal is the physical and mental symptoms that can occur when a person stops using a drug. Delusions are false beliefs that contradict reality. Hallucinations are false sensory experiences, such as seeing or hearing things that are not actually there. Both delusions and hallucinations may occur in psychotic disorders like schizophrenia. Delirium tremens are a symptom of alcohol withdrawal that can involve hallucinations, shaking, and severe confusion.

Lysergic acid diethylamide (LSD) is a hallucinogen, which means it alters the user's perception of reality and can cause psychotic symptoms. LSD use in particular can result in synesthesia, dissociation, and other hallucinogenic effects. Synesthesia is defined as experiencing one sensory experience through another sensory pathway (e.g. "seeing" music in terms of color). Contrastingly, amphetamine, cocaine, and nicotine are considered stimulants, because they speed up bodily processes.

There are many purposeful ways to induce an altered state of consciousness, but some accidental or pathological ones include infections, sleep deprivation, or psychosis. Some others are fasting, epilepsy, or traumatic experiences. An altered state of consciousness due to any of these is often an indicator of either a mental or physical health issue and should be addressed right away.

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

Priming refers to a person's ability to more quickly/accurately respond to previously asked questions, whether they remember them or not. This is closely related to the mere-exposure effect, which states that we are more likely to prefer familiar things than unfamiliar things.

The three categories of drugs that have been established are depressants, stimulants, and hallucinogens. Although an individual may seem lively with a small amount of alcohol, alcohol is actually a depressant. The liveliness comes from the fact that alcohol acts as a disinhibitor. This means it will act to slow down neural processing and brain activity responsible for judgment and inhibitions. As a result, people are more likely to act out in ways that they would not under unaffected judgment and conditions. Barbiturates are tranquilizers. These also fall under the category depressants; therefore, this would also be incorrect.

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.