The addictive potential of a drug depends on what class the drug is in. Different classes of drugs work differently in the body and brain, so some drugs are more addictive than others.
Addiction is a widespread problem. According to a report from the Substance Abuse and Mental Health Services Administration, about 21.5 millions people, ages 12 and older, had a substance use disorder in 2014. An additional 17 million people had an alcohol use disorder.
Addiction can be complicated. There are biological factors that contribute to the development of tolerance, dependency, and addiction. However, psychological factors can also contribute to the development of addiction, as people use drugs to mask emotional pain or past trauma.
While addiction was once considered a moral failing, the medical community now recognizes that it involves changes to the brain and impacts on the central nervous system. Biological factors are increasingly recognized as important considerations in recovery.
Understanding the Biology of Addiction
Addiction is considered a brain disorder, according to the National Institute on Drug Abuse (NIDA). It involves changes to the circuits in the brain that are connected to stress, rewards, and impulsive behaviors.
There are biological and environmental risk factors that make an individual more susceptible to addiction. As researchers and scientists have studied addiction over the past several decades, they have discovered many of the biological mechanisms that contribute to addiction. Genetic factors, as well as the impact of drugs in the body and brain, contribute to the development of addiction.
A drug enters the bloodstream through a variety of methods. It eventually makes its way to the brain, where it interacts with different receptors and increases the flow of certain neurotransmitters.
The specific mechanisms that a drug works within the brain depend on the kind of drug. Marijuana interacts with the cannabinoid receptors in the brain, whereas heroin interacts with the opioid receptors.
The brain sends messages between the cells when neurons release neurotransmitters, such as dopamine, serotonin, and norepinephrine, into the synapses between each cell. Drugs interact with the neurons in the brain and affect how the brain sends, receives, and processes the messages sent by those neurotransmitters.
Dopamine is a neurotransmitter that is a pleasure chemical. It’s released when stimulated by a rewarding experience. This signaling leads to a reinforcement of the behavior that caused the surge in dopamine. The brain can experience environmental triggers that signal a person to use the drug again, so the brain can experience the reward cycle again.
Some drugs activate the neurons that send these neurotransmitters through the brain because they are similar in chemical structure. They act like the brain’s existing chemicals, but they can interfere with the brain’s natural production and transmission of these chemicals. This happens with drugs like marijuana and opioids.
Other drugs can cause an overload of the natural neurotransmitters, flooding the brain with large amounts of dopamine or serotonin and then preventing the normal recycling process that the brain uses to regulate levels of these chemicals. This leads to too much of a neurotransmitter being released in the brain’s synapses. Stimulant drugs like cocaine act in this way in the brain.
What Part Of the Brain Is Affected by Drug Use?
Drugs interact with several different parts of the brain to produce addictive patterns that characterize drug abuse. In addition to the interaction with neurons and neurotransmitters in the brain, the basal ganglia, the extended amygdala, the brain stem, and the prefrontal cortex are also affected by drug use, according to the National Institute on Drug Abuse.
- Basal ganglia: This part of the brain plays a role in motivation, habits, and routine. These areas work together to create a reward response in the brain. Drugs activate this reward response, but with too much exposure, the reward circuit becomes less sensitive to the presence of the drug, reducing its effectiveness and making it less responsive to other forms of pleasure without the drug. This is why, over time, people develop a tolerance to the amount of drugs they are consuming, and they have difficulty finding pleasure in activities that don’t involve drug use.
- Prefrontal cortex: This part of the brain controls thinking, planning, decision-making, problem-solving, and impulse control. With drug use, this part of the brain can be damaged, making it harder for people to make good decisions and resist the impulse to use drugs. This is also the last part of the brain to fully develop, which is why drug use among adolescents is particularly concerning. This part of the brain can be damaged before it is even fully developed. This can result in a lifelong struggle to use good judgment and control impulsive behaviors.
- Extended amygdala: This part of the brain regulates stress and related symptoms like irritability and anxiety. When drugs provide relief from these distressful symptoms, the brain creates a reward response, and this triggers an incentive to seek out the drug again. This pattern becomes an ingrained response that becomes more hardwired into the brain with continued substance abuse over time.
- Brain stem: Some drugs, such as opioids, also affect the brain stem, which controls critical body functions like heart rate and respiratory rate. This is why drugs that impact essential body functions can be so dangerous and put the user at risk of a fatal overdose.
As you can see, the brain is a complicated system that is easily impacted by the consumption of pleasure-producing substances. The various functions in the brain work together to form a cycle that is difficult to break.
How Addictive Are the Different Classes of Drugs?
How addictive a certain class of drugs are depends on how that drug interacts with the brain and how strong the tendency toward dependency is with certain substances. Drugs that are more potent and reach the brain more quickly, and those that lead to withdrawal when the effects wear off, are the most addictive classes of drugs.
More potent forms of any drug will provide a higher risk for dependency because the potency of the drug increases the reward value in the brain. This provides a stronger reinforcement for drug-using behaviors.
Commonly abused substances differ in terms of how addictive they are.
- Cannabinoids: Drugs that interact with the cannabinoid receptors in the brain, such as marijuana, can become habit-forming, particularly when use is started in adolescence. Marijuana can cause withdrawal symptoms that include irritability, mood instability, and sleep disturbance. NIDA reports that approximately 9 percent of marijuana users will become dependent on it, and 17 percent of those who start using in the adolescent years develop marijuana dependency.
- Opioids: This class of drugs includes all opioid drugs, from prescription painkillers to illicit substances like heroin. Opioids are known to be highly addictive because they can quickly cause dependency and withdrawal symptoms that are painful when use is stopped. They also cause strong cravings for more of the drugs. The American Society of Addiction Medicine estimates that 23 percent of people who use heroin will develop an opioid addiction.
- Stimulants: This class of drugs includes prescription ADHD or narcolepsy medications as well as illicit substances like crystal meth and cocaine. The reward response created by stimulants is attributed to increases of dopamine and norepinephrine in the brain triggered by stimulant drugs. While the exact percentage of stimulants drug users who will become addicted is unknown, cocaine was involved in 422,896 emergency room visits in 2009. Other stimulants were involved in 93,562 ER visits, according to NIDA.
- Hallucinogens: Some hallucinogens interfere with the regulation of serotonin in the brain, while others interfere with the chemical glutamate. Some hallucinogens like PCP can cause withdrawal symptoms, a characteristic of addiction, while other drugs like LSD do not produce withdrawal symptoms but do cause tolerance to the drug. More research is needed to understand the addictive nature of hallucinogens.
- Alcohol: Alcohol is one of the most commonly used substances, partially because it is available legally as a recreational substance for those 21 and older. The National Institute on Alcohol Abuse and Alcoholism reports that nearly a third of adults in the U.S. will have an alcohol use disorder at some time in their lives.
What Treatment Methods Are Most Effective?
According to SAMHSA, medication-assisted treatment (MAT) is the most effective way to combat addiction to certain classes of drugs, such as opioids and alcohol. MAT works by providing medications that address the withdrawal symptoms associated with detox, minimize cravings for drugs, and increase participation in treatment programs.
Researchers are continuing to look into MAT options for the various classes of drugs. MAT is most commonly used to treat opioid addiction through the use of methadone, buprenorphine, and naltrexone. These medications work because they prevent withdrawal, control cravings, and reduce relapses.
According to a study from the journal Neuropharmacology, naltrexone is also used as a MAT for alcohol addiction because it controls cravings for alcohol and reduces the positive effects associated with alcohol consumption. While naltrexone is being explored as a potential treatment for stimulant abuse, more research in humans needs to be done before conclusive evidence supports its effectiveness for such use.
Most treatment programs will offer some combination of addiction counseling, recovery support groups, and educational programs. These are all important parts of helping people understand the nature of their addiction. Treatment gives them a place to process and heal from the psychological factors that contributed to their addiction progression.
While MAT helps people to cope with the physiological aspects of recovering from addiction to some substances, the additional structure of recovery programs gives people the information, accountability, and support they need to heal from past pain that could be contributing to their drug-seeking behaviors.
What Other Factors Contribute to Addiction?
Addiction often involves environmental and social risk factors that contribute to the use of self-medicating behaviors that can lead to dependency. People often use drugs to numb the pain of emotionally stressful situations and past traumas. This can contribute to addictive behaviors and may be a trigger for the onset of addiction.
The Following Are Some of the Environmental and Social Risk Factors That Contribute to Addiction:
- Childhood trauma and abuse
- Isolation and loneliness
- Exposure to drugs
- Other mental health problems
Having any of these experiences in your past does not mean you will become addicted to drugs, but people who experience these events are more susceptible to addiction if they do try drugs. Drug use becomes a reinforcing way to feel better when emotional pain is overwhelming.
SAMHSA reports that 39.1 percent of adults with a substance use disorder also have a mental illness. This highlights the fact that co-occurring mental health and substance use disorders can exacerbate and amplify each other.
Recovery treatment involves addressing the physiological components that contribute to addiction as well as other mental health, social, and emotional factors that are contributing to negative outcomes in an individual’s life. Treating one problem while ignoring others doesn’t help people fully recover.
Comprehensive addiction treatment will take into consideration all factors impacting the presenting problem, including exploring past traumas and addressing other mental health conditions.