Stimulants are substances that increase the activity of the central nervous system, resulting in increased blood pressure and heart rate, more alertness, and sped-up behavior and thinking. Among the most troublesome stimulants are cocaine and amphetamines, whose effects on people are very similar. When users report different effects, it is often because they have ingested different amounts of the drugs. Two other widely used and legal stimulants are caffeine and nicotine (see InfoCentral below).

Cocaine—the central active ingredient of the coca plant, found in South America—is the most powerful natural stimulant now known (Acosta, Haller, & Schnoll, 2011, 2005). The drug was first separated from the plant in 1865. Native people of South America, however, have chewed the leaves of the plant since prehistoric times for the energy and alertness the drug offers. Processed cocaine (hydrochloride powder) is an odorless, white, fluffy powder. For recreational use, it is most often snorted so that it is absorbed through the mucous membrane of the nose. Some users prefer the more powerful effects of injecting cocaine intravenously or smoking it in a pipe or cigarette.

For years people believed that cocaine posed few problems aside from intoxication and, on occasion, temporary psychosis (see Table 12-3). Like Sherlock Holmes, many felt that the benefits outweighed the costs. Only later did researchers come to appreciate its many dangers (Haile, 2012). Their insights came after society witnessed a dramatic surge in the drug’s popularity and in problems related to its use. In the early 1960s, an estimated 10,000 people in the United States had tried cocaine. Today 28 million people have tried it, and 1.6 million—most of them teenagers or young adults—are using it currently (NSDUH, 2013). In fact, 1.1 percent of all high school seniors have used cocaine within the past month and almost 2.6 percent have used it within the past year (Johnston et al., 2014).

Cocaine brings on a euphoric rush of well-being and confidence. Given a high enough dose, this rush can be almost orgasmic, like the one produced by heroin. At first cocaine stimulates the higher centers of the central nervous system, making users feel excited, energetic, talkative, and even euphoric. As more is taken, it stimulates other centers of the central nervous system, producing a faster pulse, higher blood pressure, faster and deeper breathing, and further arousal and wakefulness.

Cocaine apparently produces these effects largely by increasing supplies of the neurotransmitter dopamine at key neurons throughout the brain (Haile, 2012; Kosten et al., 2008). Excessive amounts of dopamine travel to receiving neurons throughout the central nervous system and overstimulate them. Cocaine appears to also increase the activity of the neurotransmitters norepinephrine and serotonin in some areas of the brain (Hart & Ksir, 2014; Haile, 2012).

High doses of the drug produce cocaine intoxication, whose symptoms are poor muscle coordination, grandiosity, bad judgment, anger, aggression, compulsive behavior, anxiety, and confusion. Some people have hallucinations, delusions, or both, a condition called cocaine-induced psychosis.

As the stimulant effects of cocaine subside, the user goes through a depression-like letdown, popularly called crashing, a pattern that may also include headaches, dizziness, and fainting (Acosta et al., 2011, 2005). For occasional users, the aftereffects usually disappear within 24 hours, but they may last longer for people who have taken a particularly high dose. These people may sink into a stupor, deep sleep, or, in some cases, coma.

Ingesting CocaineIn the past, cocaine use and impact were limited by the drug’s high cost. Moreover, cocaine was usually snorted, a form of ingestion that has less powerful effects than either smoking or injection (Haile, 2012). Since 1984, however, the availability of newer, more powerful, and sometimes cheaper forms of cocaine has produced an enormous increase in the use of the drug. For example, many people now ingest cocaine by freebasing, a technique in which the pure cocaine basic alkaloid is chemically separated, or “freed,” from processed cocaine, vaporized by heat from a flame, and inhaled through a pipe.

Millions more people use crack, a powerful form of freebase cocaine that has been boiled down into crystalline balls. It is smoked with a special pipe and makes a crackling sound as it is inhaled (hence the name). Crack is sold in small quantities at a fairly low cost, which has resulted in crack epidemics among people who previously could not have afforded cocaine, primarily those in poor, urban areas (Acosta et al., 2011, 2005). Around 1.1 percent of high school seniors report having used crack within the past year, down from a peak of 2.7 percent in 1999 (Johnston et al., 2014).

What Are the Dangers of Cocaine?Aside from cocaine’s harmful effects on behavior, cognition, and emotion, the drug poses serious physical dangers (Paczynski & Gold, 2011). The growth in the use of the powerful forms of cocaine has caused the annual number of cocaine-related emergency room incidents in the United States to multiply more than 125 times since 1982, from around 4,000 cases to 505,000 (SAMHSA, 2013). Cocaine use has also been linked to many suicides (Petit et al., 2012).

The greatest danger of cocaine use is an overdose. Excessive doses have a strong effect on the respiratory center of the brain, at first stimulating it and then depressing it to the point where breathing may stop. Cocaine can also create major, even fatal, heart irregularities or brain seizures that bring breathing or heart functioning to a sudden stop (Acosta et al., 2011, 2005). In addition, pregnant women who use cocaine run the risk of having a miscarriage and of having children with predispositions to later drug use and with abnormalities in immune functioning, attention and learning, thyroid size, and dopamine and serotonin activity in the brain (Minnes et al., 2014; Hart & Ksir, 2014; Kosten et al., 2008).

Amphetamines are stimulant drugs that are manufactured in the laboratory. Some common examples are amphetamine (Benzedrine), dextro-amphetamine (Dexedrine), and methamphetamine (Methedrine). First produced in the 1930s to help treat asthma, amphetamines soon became popular among people trying to lose weight; athletes seeking an extra burst of energy; soldiers, truck drivers, and pilots trying to stay awake; and students studying for exams through the night (Haile, 2012). Physicians now know the drugs are far too dangerous to be used so casually, and they prescribe them much less freely.

Amphetamines are most often taken in pill or capsule form, although some people inject the drugs intravenously or smoke them for a quicker, more powerful effect. Like cocaine, amphetamines increase energy and alertness and reduce appetite when taken in small doses; produce a rush, intoxication, and psychosis in high doses; and cause an emotional letdown as they leave the body. Also like cocaine, amphetamines stimulate the central nervous system by increasing the release of the neurotransmitters dopamine, norepinephrine, and serotonin throughout the brain, although the actions of amphetamines differ somewhat from those of cocaine (Hart & Ksir, 2014; Haile, 2012).

One kind of amphetamine, methamphetamine (nicknamed crank), has surged in popularity in recent years and so warrants special focus. Almost 6 percent of all people over the age of 11 in the United States have used methamphetamine at least once. Around 0.2 percent use it currently (NSDUH, 2013). It is available in the form of crystals (also known by the street names ice and crystal meth), which users smoke.

Most of the nonmedical methamphetamine in the United States is made in small “stovetop laboratories,” which typically operate for a few days in a remote area and then move on to a new—safer—location (Hart & Ksir, 2014). Such laboratories have been around since the 1960s, but they have increased eightfold—in number, production, and in being confiscated by authorities—over the past decade. A major health concern is that the secret laboratories expel dangerous fumes and residue (Burgess, 2001).

Since 1989, when the media first began reporting about the dangers of smoking methamphetamine crystals, the rise in usage has been dramatic. Until recently, it had been much more prevalent in western parts of the United States, but its use has now spread east as well. Methamphetamine-linked emergency room visits are rising in hospitals throughout all parts of the country (SAMHSA, 2013).

Methamphetamine is about as likely to be used by women as men. Around 40 percent of current users are women (NSDUH, 2013). The drug is particularly popular today among biker gangs, rural Americans, and urban gay communities and has gained wide use as a “club drug,” the term for those drugs that regularly find their way to all night dance parties, or “raves” (Hart & Ksir, 2014; Hopfer, 2011).

Like other kinds of amphetamines, methamphetamine increases activity of the neurotransmitters dopamine, serotonin, and norepinephrine, producing increased arousal, attention, and related effects (Acosta et al., 2011, 2005; Dean & London, 2010). It can have serious negative effects on a user’s physical, mental, and social life. Of particular concern is that it damages nerve endings, a problem called neurotoxicity. But users focus more on methamphetamine’s immediate positive impact, including perceptions by many that it makes them feel hypersexual and uninhibited (Washton & Zweben, 2008; Jefferson, 2005).

Regular use of either cocaine or amphetamines may lead to stimulant use disorder. The stimulant comes to dominate the person’s life, and the person may remain under the drug’s effects much of each day and function poorly in social relationships and at work. Regular stimulant use may also cause problems in short-term memory and attention (Lundqvist, 2010; Kubler et al., 2005). People may develop tolerance and withdrawal reactions to the drug—in order to gain the desired effects, they must take higher doses, and when they stop taking it, they may go through deep depression, fatigue, sleep problems, irritability, and anxiety (Barr et al., 2011; Hill & Weiss, 2011). These withdrawal symptoms can last for weeks or even months after drug use has ended. In a given year, 0.4 percent of all people over the age of 11 display stimulant use disorder that is centered on cocaine, and 0.2 percent display stimulant use disorder centered on amphetamines (NSDUH, 2013).

Caffeine is the world’s most widely used stimulant. Around 80 percent of the world’s population consumes it daily. Most of this caffeine is taken in the form of coffee (from the coffee bean); the rest is consumed in tea (from the tea leaf), cola (from the kola nut), so-called energy drinks, chocolate (from the cocoa bean), and numerous prescription and over-the-counter medications, such as Excedrin.

Around 99 percent of ingested caffeine is absorbed by the body and reaches its peak concentration within an hour. It acts as a stimulant of the central nervous system, again producing a release of the neurotransmitters dopamine, serotonin, and norepinephrine in the brain (Advokat et al., 2014; Cauli & Morelli, 2005). Thus it raises a person’s arousal and motor activity and reduces fatigue. It can also disrupt mood, fine motor movement, and reaction time and may interfere with sleep (Hart & Ksir, 2014; Juliano, Anderson, & Griffiths, 2011; Judelson et al., 2005). At high doses, it increases gastric acid secretions in the stomach and the rate of breathing.

More than two to three cups of brewed coffee (250 milligrams of caffeine) can produce caffeine intoxication, which may include such symptoms as restlessness, nervousness, anxiety, stomach disturbances, twitching, and a faster heart rate (Juliano et al., 2011; Paton & Beer, 2001). Doses larger than 10 grams of caffeine (about 100 cups of coffee) can cause grand mal seizures and fatal respiratory failure.

Many people who suddenly stop or cut back on their usual intake of caffeine—even those whose regular consumption is low (two and a half cups of coffee daily or seven cans of cola)—have withdrawal symptoms. One pioneering study had adult participants consume their usual caffeine-filled drinks and foods for 2 days, then abstain from all caffeine-containing foods for 2 days while taking placebo pills that they thought contained caffeine, and then abstain from such foods for 2 days while taking actual caffeine pills (Silverman et al., 1992). More participants had headaches (52 percent), depression (11 percent), anxiety (8 percent), and fatigue (8 percent) during the 2-day placebo period than during the caffeine periods. In addition, people reported using more unauthorized medications (13 percent) and they performed experimental tasks more slowly during the placebo period than during the caffeine periods.

Although DSM-5 acknowledges that many people go through caffeine intoxication and caffeine withdrawal, it does not go so far as to list caffeine use disorder as an official category (APA, 2013). Instead, it views this disorder as a condition that has received some support in clinical studies and that may warrant official classification in a future edition of the DSM, depending on the outcome of future studies. If added to the DSM, they key criteria for this disorder would be a 1-year pattern of problematic caffeine use, unsuccessful efforts to reduce caffeine use, awareness that one’s continued caffeine use is causing a repeated physical or psychological problem, withdrawal symptoms if one stops caffeine use, and significant impairment or distress.

Investigators often assess caffeine’s impact by measuring coffee consumption, yet coffee also contains other chemicals that may be dangerous to a person’s health. Although some early studies hinted at links between caffeine and cancer (particularly pancreatic cancer), the evidence is not conclusive (Hart & Ksir, 2014; Juliano et al., 2011). On the other hand, studies do suggest that there may be correlations between high doses of caffeine and heart rhythm irregularities (arrhythmias), high cholesterol levels, and risk of heart attacks (Hart & Ksir, 2014). And some, but not all, studies raise the possibility that very high doses of caffeine during pregnancy may increase the risk of miscarriage (Brent et al., 2011; Weng et al., 2008). As public awareness of these possible health risks has increased, caffeine consumption has declined and the consumption of decaffeinated drinks has increased over the past few decades. There are, however, indications that caffeine consumption may currently be on the rise once again.