RETRIEVAL PRACTICE Take a moment to answer each of these Learning Objective Questions (repeated here from within this section). Then click the 'show answer' button to check your answers. Research suggests that trying to answer these questions on your own will improve your long-term retention (McDaniel et al., 2009).

Those with a substance use disorder may exhibit impaired control, social disruption, risky behavior, and the physical effects of tolerance and withdrawal. Psychoactive drugs alter perceptions and moods. They may produce tolerance—requiring larger doses to achieve the desired effect—and withdrawal—significant discomfort accompanying attempts to quit. Continued use may lead to addiction, which is the compulsive craving of drugs or certain behaviors (such as gambling) despite known adverse consequences.

Psychologists debate whether the concept of addiction has been stretched too far, and whether addictions are really as irresistible as commonly believed. Addictions can be powerful, and many with addictions do benefit from therapy or group support. But viewing addiction as an uncontrollable disease can undermine people’s self-confidence and their belief that they can change. The addiction-as-disease-needing-treatment idea has been extended to a host of excessive, driven behaviors, but labeling a behavior doesn’t explain it. The concept of addiction continues to evolve, as psychiatry’s manual of disorders now includes behavior addictions such as “gambling disorder” and proposes “Internet gaming disorder” for further study.

Depressants, such as alcohol, barbiturates, and the opiates, dampen neural activity and slow body functions. Alcohol tends to disinhibit, increasing the likelihood that we will act on our impulses, whether harmful or helpful. It also impairs judgment, disrupts memory processes by suppressing REM sleep, and reduces self-awareness and self-control. User expectations strongly influence alcohol’s behavioral effects.

Stimulants—including caffeine, nicotine, cocaine, the amphetamines, methamphetamine, and Ecstasy—excite neural activity and speed up body functions, triggering energy and mood changes. All are highly addictive. Nicotine’s effects make smoking a difficult habit to kick, yet the percentage of Americans who smoke has been dramatically decreasing. Cocaine gives users a fast high, followed within an hour by a crash. Its risks include cardiovascular stress and suspiciousness. Use of methamphetamines may permanently reduce dopamine production. Ecstasy (MDMA) is a combined stimulant and mild hallucinogen that produces euphoria and feelings of intimacy. Its users risk immune system suppression, permanent damage to mood and memory, and (if taken during physical activity) dehydration and escalating body temperatures.

Hallucinogens—such as LSD and marijuana—distort perceptions and evoke hallucinations—sensory images in the absence of sensory input. The user’s mood and expectations influence the effects of LSD, but common experiences are hallucinations and emotions varying from euphoria to panic. Marijuana’s main ingredient, THC, may trigger feelings of disinhibition, euphoria, relaxation, relief from pain, and intense sensitivity to sensory stimuli. It may also increase feelings of depression or anxiety, impair motor coordination and reaction time, disrupt memory formation, and damage lung tissue (because of the inhaled smoke).

Some people may be biologically vulnerable to particular drugs, such as alcohol. Psychological factors (such as stress, depression, and hopelessness) and social factors (such as peer pressure) combine to lead many people to experiment with—and sometimes become addicted to—drugs. Cultural and ethnic groups have differing rates of drug use. Each type of influence—biological, psychological, and social-cultural—offers a possible path for drug misuse prevention and treatment programs.