Types of Psychoactive Drugs
Drugs that alter consciousness are called psychoactive drugs. These drugs typically work by influencing or mimicking activity in neurotransmitters, chemicals that communicate messages between neurons. Some psychoactive drugs are used to treat medical or psychological conditions. Others, such as caffeine, nicotine, alcohol and illegal drugs, are used mostly for recreational purposes. Misuse of drugs, even legal drugs and prescribed medications, can cause physical health problems, mental health problems, harm to oneself and others, and legal difficulties.
The main categories of psychoactive drugs are depressants, opiates, stimulants, and hallucinogens. Depressants, such as alcohol and sedatives, are psychoactive drugs that reduce neural activity and slow bodily functions. Depressants can reduce anxiety, decrease social inhibitions, and impair judgment. Alcohol consumption is linked to increased risk for aggressive behavior. Because depressants impair coordination and perception, they increase risk for car accidents and accidental injuries.
Stimulants, such as caffeine, nicotine, cocaine, and amphetamines, are psychoactive drugs that increase neural activity and accelerate bodily functions. They increase heart rate, reduce hunger, boost mood, and speed thinking. Smoking or injecting stimulant drugs produces a faster reaction than swallowing stimulant drugs. The risk of addiction is highest for fast-acting forms of stimulants.
Opiates, such as morphine and oxycodone, reduce pain. Opiates, also called narcotics, are highly addictive. Some people become addicted after taking prescribed opiates to manage pain. This class of drugs carries the highest risk of accidental overdose. Withdrawal from opiates can be extremely uncomfortable, with symptoms including nausea, vomiting, diarrhea, chills, and sweating. Because opiates mimic the body's natural pain-killing neurotransmitters, regular use can lead to lasting changes in how the brain and body manage pain. Opiate addiction is often treated with long-term maintenance doses of mild opiates, such as methadone.
Hallucinogens, also called psychedelics, distort perceptions and trigger hallucinations. This class of drugs includes LSD, Ecstasy, mescaline, and marijuana. Federal restrictions have made it difficult to conduct research on hallucinogens. A small number of studies suggest that hallucinogenic drugs may have potential benefits in the treatment of physical or psychological problems.
Biological Aspects of Addiction
Many psychoactive drugs carry a risk for addiction—compulsive use of a substance despite harmful consequences. Even people who do not have a substance abuse disorder can demonstrate drug dependence, in which drug tolerance and withdrawal symptoms are experienced if the drug is not taken. For example, cancer patients may depend on pain medication to reduce their suffering. The body can adapt to these drugs, requiring larger doses to relieve the pain, and patients can experience a recurrence or increase in pain if the pain medication is stopped.
Biological factors increase risk for addiction. The brain's reward circuitry consists of clusters of neurons that release the neurotransmitter dopamine. They are concentrated in the prefrontal cortex and certain areas of the midbrain. Any pleasurable activity (from eating to sex to hearing a favorite song) activates these circuits.
Different people have different types and ratios of dopamine receptors. Some people are born with fewer receptors. This makes them more prone to addiction because normal amounts of dopamine are not enough to produce pleasure. Risk-taking, exciting activities, and psychoactive drugs boost the release of dopamine, making them especially appealing for people with an underactive reward system. Genes play a role in the development and function of the brain's reward system. Prenatal exposure to alcohol, nicotine, or illegal drugs can influence the development of this system, increasing risk for future addiction. Babies whose mothers use drugs while pregnant can be born addicted to drugs.The Impact of Repeated Drug Use on Neurons in the Brain's Reward Pathways
Drug Tolerance
Learned Aspects of Addiction
According to the opponent process theory of drug addiction, classical conditioning influences drug tolerance and relapse. The opponent process theory suggests that the pleasurable feelings that follow drug use decrease over time. Gradually, individuals need to use more of the drug to achieve the same high. In classical conditioning, repeating pairing of stimuli (events or actions) results in a learned association. An individual may begin to crave a cigarette on the way home from work because he always smokes in the car on the way home. The body also uses environmental cues to predict drug intake. The smell and taste of coffee triggers physical changes even before caffeine takes effect. For drugs that lower pain sensitivity, the body temporarily increases pain sensitivity in response to drug-related cues (e.g., a syringe). This is the brain's way of trying to keep the body in homeostasis, or a state of balance.
When a person who takes drugs regularly takes their usual dose in unfamiliar surroundings, the learned drug-related cues are not present. Thus, the brain does not trigger compensatory physical responses, and the addict can suffer an overdose. In one study, 70 percent of heroin addicts receiving emergency treatment for overdoses had not taken more than their usual dose, but they had taken the drug in new surroundings.
If the addict's environment contains drug-related cues but the drug is not consumed, the person can experience withdrawal symptoms. For instance, former addicts have been found to display physiological signs of withdrawal when watching a video of drug preparation months or even years after they stopped using. Former alcoholics may experience intense cravings and withdrawal symptoms when they enter bars.
This is why it is much easier for people to overcome addiction in new environments, such as drug rehabilitation centers. The cues are not there, so the cravings subside. But when addicts return to their old environments, the cues are there, the cravings return full force, and they often relapse.
Environmental Risk Factors for Addiction
Not every person who uses alcohol, nicotine, or illegal drugs will become addicted. Most people who become addicted to drugs begin use in adolescence. This is one reason laws have restricted the sale of nicotine products to minors and banned advertisements targeting teenage users.
Some studies suggest that people who ultimately develop drug addictions are likely to use marijuana before other illicit drugs. This has led to suggestions that marijuana is a gateway to more harmful drugs. However, the gateway assumption may seem true simply because marijuana is relatively easy to access compared to more harmful drugs. Most people who use marijuana do not begin to use more harmful substances. Given that marijuana is the most commonly used illegal drug (and legal in Canada and several U.S. states), it is not surprising that it is often the first illegal drug people try.
Both personal and environmental factors increase risk for addiction. Having an impulsive, risk-taking personality increases risk. It makes people likely to try drugs at a younger age and to experiment with more addictive drugs. Addiction is also linked to a tendency to focus on immediate rewards rather than long-term gains. Finally, individuals who are prone to depression or anxiety may use drugs or alcohol as a coping mechanism. For example, individuals may drink to numb feelings of pain or to decrease their inhibitions (shyness) around others.
Key environmental factors include access, modeling, and life stress. Easy access to drugs increases risk for both experimentation and addiction. The modeling of substance use by others also matters. Teenagers are more likely to try drugs if substance use is common in their family or peer group. Life stress and lack of parental supervision also increase risk for substance use problems.