Psychoactive Drugs and Substance Use Disorder

Learning Objectives

  • Describe how substance abuse disorders are diagnosed

Substance Abuse Disorders

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. Drug categories listed in the DSM-5 include those for alcohol, opioids, depressants, stimulants, hallucinogens, inhalants, and other or unknown substances. 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. For 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. Negative 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. Dependence levels are 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.

In the DSM-5, each category of drugs has a use disorder listed, such as alcohol use disorder or opioid use disorder (further categorized as mild, moderate, or severe). Each drug category also lists an intoxication disorder, such as alcohol intoxication or cannabis intoxication, and a withdrawal disorder, such as alcohol withdrawal or opioid withdrawal. Intoxication disorders are attributed to recent drug use that causes significant and problematic psychological or behavioral changes. Withdrawal disorders are caused by clinically significant behavioral or psychological changes that occur after the cessation of drug abuse.

Watch It

All the substance use disorders we’ll learn about in this module share similar characteristics, but vary depending on the drug that causes the addiction. In general terms, those who suffer from a substance use disorder share these common characteristics. They do the following:

  • develop a tolerance for the drug
  • experience withdrawal symptoms when the substance leaves their body
  • take risks because of the substance
  • spend a lot of time thinking about the drug
  • stop doing meaningful things and withdraw from activities and others
  • take more of the drug than they intended to
  • crave the drug
  • struggle to quit

You can view the transcript for “Substance Use Disorder” here (opens in new window).

Link to Learning

Read through this fascinating comic created by Stuart McMillen about psychologist 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. There are many psychoactive drugs, and their relationships are shown in Figure 1. 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 will learn more about these types of 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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depressant: drug that tends to suppress central nervous system activity

hallucinogen: one of a class of drugs that results in profound alterations in sensory and perceptual experiences, often with vivid hallucinations

physical dependence: changes in normal bodily functions that cause a drug user to experience withdrawal symptoms upon cessation of use

psychoactive drugs: chemical substances that alters brain functioning, causing changes to consciousness, perception, mood, and thoughts

psychological dependence: emotional, rather than a physical, need for a drug that may be used to relieve psychological distress

stimulant: drug that tends to increase overall levels of neural activity, including caffeine, nicotine, amphetamines, and cocaine

substance use disorder: DSM-5 diagnosis for those who show a compulsive pattern of drug use associated with both physical and psychological dependence

tolerance: state of requiring increasing quantities of the drug to gain the desired effect

withdrawal: variety of negative symptoms experienced when drug use is discontinued