Types of Psychoactive Drugs
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
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
Learned Aspects of Addiction
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
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.