Introduction to Drugs and behavior/Psychopharmacology - Part 1

Psychopharmacology - What is it?

To learn more about psychopharmacology, please check out "Psychopharmacology: Drugs, the Brain, and Behavior," by Jerrold S. Meyer and Linda F. Quenzer.

Psychopharmacology is defined as the study of how drugs affect mood, thinking, and behavior (1). Thus, in this introduction, we will explore the effects and the processing of drugs from a biopsychological perspective. First, we have to define some of the terminology. We will start with what a drug is. In one of part of our introduction to biopsychology (, we learned that a drug is a chemical that comes from the outside of our bodies and changes the normal functions of the cells when taken in low doses (2). The changes produced on a molecular level when a drug binds to the receptor of a neuron are called drug action (3). But the changes that occur on a physiological and/or psychological level are called drug effects. To give you an example that will mark the differences between drug action and drug effect we will cover two drugs: atropine and morphine. The former affects the eye by dilatating the pupil (this is the drug effect) when applied to the eye muscles of the iris (this would be the site of the drug action). Morphine also has the same drug effect (widening the pupil), but not the same site of drug action (nothing happens if applied to the eye, but the drug effect occurs when the morphine is taken internally). We will cover more specific drug effects later. Right now we have to explore four branches of effects. They are: 

  • Therapeutic effects: These are desired physiological or psychological changes. For example, when a teenager takes an antidepressant, he or she expects that some of the symptoms that belong to major depressive disorder disappear.
  • Side effects: These are all the changes that were not therapeutic. In other words, the undesired changes in the body and mental processes. To use the example above, side effects would be how the risk of suicide doubles for teenagers when they take an antidepressant rather than a placebo (4).
  • Specific drug effects: These are effects that are dependent on the physiology of the person or animal.
  • Nonspecific drug effects: These are the effects that instead of depending on the biochemistry of an individual, they rely on the individual's background. An example of something that depends greatly on an individual's background instead of the physiology of the person is a placebo (this is a sugar pill). This pill can have therapeutic and side effects that belong to other drugs, even if it the placebo does not have the biochemical interaction that causes the other drugs to produce those effects.

Placebos are important because they are used to understand how much of the drug effects are caused by the individual's expectations and how much by the biochemical interaction of the drug. Thus, when researchers do an experiment with drugs (with drugs, not on drugs), or an experiment in general, they divide their test subjects into at least two groups: control and experimental groups. The former gets the placebo and the latter the drug, but neither groups is aware of what they were given. Because of the influence of the placebo and other factors, psychopharmacologists usually engage in a type of study called double blind procedure. This is similar to the set up of the experiment mentioned above. However, in this case, neither the participant nor the researcher knows which group received the drug or the placebo. This helps eliminate the expectations that influence test results by both parties.

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1. "Psychopharmacology: Drugs, the Bran, and Behavior," by Jerrold S. Meyer and Linda F. Quenzer.

2. "Physiology of Behavior" by Neil Carson