Depressants are broadly defined as drugs that decrease activity in the nervous system.Many depressants are available to us; one is alcohol, a widely used recreational drug in many countries, but also widely used by people as a way of managing their own stress and anxiety. Other depressants are commonly prescribed by physicians; these drugs include medications (e.g., zolpidem) given to people who have trouble sleeping, and drugs (usually benzodiazepines, such as Valium or Xanax) used to treat anxiety.
Depressants are helpful in many circumstances—but if they’re misused or overused, they can lead to serious medical and psychological difficulties. For example, both the benefits and the problems associated with alcohol are well documented. At low doses, alcohol produces feelings of pleasure and well-being. But alcohol also depresses activ-ity in neural circuits that ordinarily control our impulses, and when these (inhibitory) circuits are less active, people are likely to engage in a wide range of behaviors they would ordinarily avoid. If provoked, they’re more likely to be aggressive. If tempted toward sexual behavior, they’re more likely to give in to the temptation. But the same mechanisms can also promote positive behaviors. For example, people asked for charitable donations are more likely to say yes if they’ve had a drink or two; restaurant customers are more likely to leave generous tips after they’ve enjoyed a bottle of wine.
This relaxation of inhibition can, of course, create enormous dangers. Thus, people who understand perfectly well the dangers of driving an automobile while drunk may still get behind the wheel of a car—thanks, in large part, to impairment in brain circuits that would ordinarily forbid such behavior. Then, once the person is behind the wheel, alcohol’s other effects come into play—slower reaction times, poor coordination, and impaired decision making. All of this makes it easy to understand why, according to annual surveys by the National Highway Traffic Safety Administration, almost half of the deaths from traffic accidents in the United States involve alcohol consumption. Similar data have been reported in many other countries.
Researchers have further suggested that alcohol produces a narrowing of attention, so that people who have been drinking pay attention to a diminished set of cues in the envi-ronment and a smaller set of considerations from memory (Steele & Josephs, 1990). As a result, the drinker’s thinking is very much tied to the here and now, and he pays little atten-tion to the possible consequences of his actions. This helps us understand why, for exam-ple, college students are less likely to use condoms if they’ve been drinking—apparently, in this setting, students pay less attention to the obvious dangers associated with unprotected sex (MacDonald, Zanna, & Fong, 1996; MacDonald, Cohen, Stenger, & Carter, 2000). This shortsighted thinking may also help explain why, according to one estimate, alcohol is involved in 90% of the rapes and a similar proportion of the violent crimes occurring on college campuses (Wechsler, Davenport, Dowdall, Moeykens, & Castillon, 1994).
We should add, though, that alcohol’s effects derive from a mix of the drug’s actual impact on brain chemistry and people’s expectations about its effects. In one study, half of the partic-ipants consumed an alcoholic drink and half consumed an alcohol-free drink (Abrams & Wilson, 1983; also see Goldman, Brown, & Christiansen, 1987). In each group, half of the participants thought they had consumed alcohol and half believed there was no alcohol in the drink. (The taste of the drink, for all participants, made it impossible for them to detect the alcohol, and so their beliefs about the drink depended entirely on what the experimenter told them.) All participants were then shown an erotic movie, and those who thought they had consumed alcohol (whether they actually had or not) reported stronger sexual fantasies in response to the film and reported feeling less guilt about these fantasies. Alcohol, it seems, can release someone’s impulses through psychological means as well as pharmaceutical ones.
What about the other depressants—sleeping pills or the various antianxiety drugs? These are highly effective if used appropriately, but they can also produce physical and psy-chological dependence, making withdrawal symptoms after prolonged use quite likely; the symptoms can include enhanced anxiety (a “rebound” effect), insomnia, or even seizures. In addition, people who’ve been taking these drugs for a long time often become less sen-sitive to the medication—a pattern known as drug tolerance—and so need a higher and higher dose to achieve the same effects. Unfortunately, at higher doses these drugs have further effects: High doses of benzodiazepines, for example, can cause cognitive impair-ment and, especially if combined with alcohol, can push the person into a coma.