Why Is Milk White?: & 200 Other Curious Chemistry Questions (2013)
4. Health and Safety
What are some chemicals that make people crazy?
Psychologists use the term psychosis instead of “crazy.” The brain works by using chemicals to send signals between nerve cells. As mentioned in chapter 1, these chemicals are called neurotransmitters. If a person has a lack of some neurotransmitters or an excess of one or more neurotransmitters, they may perceive things differently from other people.
One example of this is hallucinations, where they see or hear things that are not there. But other examples are more common, such as depression and bipolar disorders, where the person feels sad or irritable or has an elevated arousal or energy level.
Some drugs affect the same receptors in the brain that natural neurotransmitters affect. This is why they have effects on the brain and why we use them to make up for a lack of a neurotransmitter in people whose bodies aren’t making enough. Other drugs block the receptors that neurotransmitters use, so the person experiences the same effects as if they had little or none of the neurotransmitter.
Drugs that can strongly affect how the brain reacts to neurotransmitters are called psychotomimetic drugs. This just means that they mimic the effects of psychosis. Often these drugs are used (or abused) in small doses that do not trigger psychotic effects or behavior, but if taken in large doses the effects can be disabling.
An example is tetrahydrocannabinol, the active ingredient in marijuana. In massive doses taken intravenously, it affects the cannabinoid receptors in the brain to such an extent that symptoms of schizophrenia develop. Some opiates are also psychotomimetic, such as pentazocine and butophanol. Other alkaloids that can be psychotomimetic are scopolamine, atropine, diphenhydramine, phencyclidine, and dextromethorphan. Psychotomimetic drugs may cause symptoms of depression or euphoria and dreamlike states in which things are not clear and sharp.