States of Consciousness

Psychoactive Drugs and Addiction

Learning Objectives

  • Describe how substance abuse disorders are diagnosed

Substance Abuse Disorders

The fifth edition of the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) is used by clinicians to diagnose individuals suffering from various psychological disorders. Drug use disorders are addictive disorders, and the criteria for specific substance (drug) use disorders are described in DSM-5. A person who has a substance use disorder often uses more of the substance than they originally intended to and continues to use that substance despite experiencing significant adverse consequences. In individuals diagnosed with a substance use disorder, there is a compulsive pattern of drug use that is often associated with both physical and psychological dependence.

Physical dependence involves changes in normal bodily functions—the user will experience withdrawal from the drug upon cessation of use. In contrast, a person who has psychological dependence has an emotional, rather than physical, need for the drug and may use the drug to relieve psychological distress. Tolerance is linked to physiological dependence, and it occurs when a person requires more and more drug to achieve effects previously experienced at lower doses. Tolerance can cause the user to increase the amount of drug used to a dangerous level—even to the point of overdose and death.

Drug withdrawal includes a variety of negative symptoms experienced when drug use is discontinued. These symptoms usually are opposite of the effects of the drug. For example, withdrawal from sedative drugs often produces unpleasant arousal and agitation. In addition to withdrawal, many individuals who are diagnosed with substance use disorders will also develop tolerance to these substances. Psychological dependence, or drug craving, is a recent addition to the diagnostic criteria for substance use disorder in DSM-5. This is an important factor because we can develop tolerance and experience withdrawal from any number of drugs that we do not abuse. In other words, physical dependence in and of itself is of limited utility in determining whether or not someone has a substance use disorder.

Link to Learning

Read through this fascinating comic created by Stuart McMillen about psychologist’s Bruce Alexander’s Rat Park study on addiction.

For more information on Bruce Alexander’s study and a better understanding of addiction, listen to Johann Hari’s TED Talk, “Everything you think you know about addiction is wrong.”

Drug Categories

The effects of all psychoactive drugs occur through their interactions with our endogenous neurotransmitter systems. Many of these drugs, and their relationships, are shown in Figure 1. As you have learned, drugs can act as agonists or antagonists of a given neurotransmitter system. An agonist facilitates the activity of a neurotransmitter system, and antagonists impede neurotransmitter activity.

The main categories of drugs are depressants, stimulants, and hallucinogens. You’ll learn more about these types drugs in the coming pages.

Four main drug categories are identified by differently colored circles showing overlaps: the four main drug categories are “antipsychotics,” “stimulants,” “depressants,” and “hallucinogens.” The circle titled “Antipsychotics” includes the drug names “Haldol,” “Risperdal,” and “Seroquel.” The circle titled “Stimulants” contains a subcircle titled “Psychmotor stimulants” with the drug names “Amphetamines,” “Khat,” “Ritalin,” and “Cocaine.” The “Stimulants” circle contains another subcircle titled “Methylxanthines” with the drug names “Caffeine,” “Theophylline,” and “Theobromine.” The circle titled “Depressants” contains a subcircle titled “Sedative Hypnotics” with the drug names “Alcohol,” “Barbituates,” “Ether,” and “GHB”; within that circle is a subcircle titled “Minor tranquilizers” with the drug names “Ativan,” “Valium,” and “Xanax.” “Nicotine” falls in the overlap between the “Stimulants” and “Depressants” circles. The circle titled “Depressants” also contains a subcircle titled “Narcotic Analgesics” with the drug names “Opium,” “Codeine,” “Morphine,” “Heroin,” and “DXM.” “DXM” falls in the overlap between the “Depressants” circle and the “Dissociatives” subcircle of the “Hallucinogens” circle. The circle titled “Hallucinogens” contains a subcircle labeled “Dissociatives” including the drug names ”Ketamine,” “PCP,” “Nitrous,” “Amanitas,” and “Salvinorum.” Within that subcircle, “Ketamine,” “PCP,” and “Nitrous” overlap with with the “depressants” circle The circle titled “Hallucinogens” also contains a subcircle titled “Psychadelics” including the drug names “MDMA,” “Mescaline,” “LSD,” “Psilocybin,” “AMT,” “DMT,” and “Ibogaine.” Within that subcircle, “MDMA,” “Mescaline,” “LSD,” “Psilocybin,” and “AMT” fall within the overlap between the “Hallucinogens” and “Stimulants” circles. “Ibogaine” falls within the overlap between the “Psychadelics” and “Dissociatives” subcircles. Outside of all subcircles, “Marijuana” falls within the overlap between the “Stimulants,” “Depressants,” and “Hallucinogens” circles.
Figure 1. This figure illustrates various drug categories and overlap among them. (credit: modification of work by Derrick Snider)
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