Drug abuse spans a wide range of substances, from illegal drugs like heroin and cocaine to prescription medications, over-the-counter products, and even common household chemicals. In 2024, about 48.2 million people aged 12 or older in the United States used an illicit drug in the past month. Understanding the major categories and specific examples can help you recognize the risks associated with each.
Opioids
Opioids are one of the most widely abused and dangerous drug categories. They work by attaching to receptors in the brain and body that control pain and pleasure, flooding the system with dopamine. Prescription opioids commonly involved in abuse include hydrocodone (Vicodin), oxycodone (OxyContin, Percocet), morphine, codeine, and fentanyl. These are legitimately prescribed for pain but carry high addiction potential when taken in larger amounts than directed or without a prescription.
Heroin, an illegal opioid never used medically in the United States, remains a major concern. But the biggest driver of overdose deaths in recent years has been synthetic opioids like fentanyl. In 2023, synthetic opioids were involved in nearly 72,800 overdose deaths. That number dropped significantly to about 47,700 in 2024, a 35.6% decrease, though the toll remains enormous. Fentanyl is 50 to 100 times more potent than morphine, and illicitly manufactured versions frequently contaminate other street drugs, making any use unpredictable and potentially fatal. In 2024, roughly 7.8 million people misused opioids.
Stimulants
Stimulants increase the activity of brain chemicals involved in energy, focus, and reward. Cocaine and methamphetamine are the most commonly abused illegal stimulants. Cocaine blocks the recycling of dopamine in the brain, keeping levels artificially high. Methamphetamine, sometimes called crystal, ice, or crank, works differently: it actively pushes extra dopamine into the spaces between brain cells, producing an intense and long-lasting high. Meth is inexpensive and can be manufactured from over-the-counter ingredients, which has fueled widespread abuse.
Prescription stimulants are also frequently misused. Medications containing amphetamine or methylphenidate, prescribed for ADHD, narcolepsy, and sometimes weight management, are taken by people without a prescription or in doses higher than directed. College students and young professionals sometimes abuse these drugs seeking improved concentration or productivity, but misuse carries risks of anxiety, irregular heartbeat, and dependence.
Central Nervous System Depressants
Depressants slow brain activity by boosting the effects of a brain chemical called GABA, which essentially puts the brakes on neural signaling. This produces sedation, relaxation, and reduced anxiety. The category includes three main groups:
- Benzodiazepines such as diazepam (Valium), alprazolam (Xanax), and clonazepam (Klonopin), prescribed for anxiety and panic attacks. They carry a high risk of tolerance, dependence, and addiction, which is why doctors typically avoid prescribing them long-term.
- Sleep medications known as “z-drugs,” including zolpidem (Ambien), eszopiclone (Lunesta), and zaleplon, prescribed for insomnia. Though designed to be safer than older sedatives, they still carry abuse potential.
- Barbiturates such as phenobarbital and pentobarbital, which are used less frequently today because the gap between an effective dose and a lethal dose is dangerously narrow.
One serious risk with depressant abuse is withdrawal. Because these drugs suppress brain activity, stopping suddenly can cause a rebound effect that includes seizures, which can be life-threatening.
Hallucinogens and Dissociatives
About 10.4 million people in the United States used hallucinogens in the past year as of 2024. Classic hallucinogens like LSD and psilocybin (the active compound in “magic mushrooms”) distort perception dramatically. Users may see brighter colors, hear sharper sounds, experience time slowing down, or even “hear” colors and “see” sounds, a blending of senses known as synesthesia. These drugs alter the activity of serotonin pathways in the brain.
Dissociative drugs work differently. PCP (angel dust), ketamine, and DXM (dextromethorphan, found in cough medicines) disrupt a brain chemical called glutamate, which plays a key role in learning, memory, emotion, and pain perception. The result is a feeling of floating, detachment from your body, and distorted sight and sound. At high doses, dissociatives can cause extreme confusion, paranoia, and loss of motor control.
Club Drugs
Several drugs are grouped together because they’re commonly used at bars, concerts, clubs, and parties. MDMA (ecstasy or molly) is a hallucinogenic stimulant chemically similar to both methamphetamine and mescaline. It produces feelings of emotional closeness, energy, and heightened sensory experiences. GHB (sometimes called liquid ecstasy) is an anesthetic that produces a pleasurable intoxication and has also been used as a sleep aid and by bodybuilders as a supposed growth promoter.
Both GHB and flunitrazepam (Rohypnol) have been linked to drug-facilitated sexual assaults because they can be slipped into drinks, causing sedation and memory loss. Ketamine, another anesthetic, also appears in club settings for its dissociative, dreamlike effects.
Inhalants
Inhalant abuse involves breathing in fumes from ordinary household products to get high. It’s particularly common among adolescents because these substances are cheap and easily accessible. The most commonly abused inhalants reported to U.S. poison centers include gasoline (41% of cases), paint (13%), propane and butane (6%), and air fresheners (6%). Other frequently abused products include felt-tip markers, correction fluid, rubber cement, computer cleaning sprays, whipped cream canisters (for nitrous oxide, known as “whippets”), and nail polish remover.
Inhalant abuse is uniquely dangerous because of “sudden sniffing death syndrome,” the leading cause of death among inhalant abusers. Inhaled chemicals disrupt the heart’s electrical system and make it hypersensitive to adrenaline. A user who gets startled while inhaling, such as being caught by a parent, can experience a fatal heart rhythm disturbance. This can happen even on a first use.
Over-the-Counter Medications
Two over-the-counter medications are most commonly abused. Dextromethorphan (DXM), a cough suppressant found in many cold medicines, produces effects ranging from mild stimulation at low doses to hallucinations and a feeling of physical distortion at high doses, similar to PCP or ketamine. The practice of drinking large amounts of cough syrup is sometimes called “robo-tripping.” Health risks include poor motor control, dangerously elevated blood pressure, slurred speech, and extreme panic or aggression. Products containing acetaminophen alongside DXM pose an additional risk of severe liver damage.
Loperamide, the active ingredient in anti-diarrheal medications, is an opioid designed not to cross into the brain at normal doses. But people sometimes take massive quantities to produce euphoria or to manage opioid withdrawal symptoms. At these doses, loperamide can cause erratic heartbeat, kidney problems, fainting, and loss of consciousness. Overdose on either DXM or loperamide can be fatal.
Anabolic Steroids
Anabolic steroids are synthetic versions of testosterone used medically to treat hormonal deficiencies, but they’re abused by athletes, bodybuilders, and recreational gym-goers seeking muscle growth and improved performance. Commonly encountered steroids include testosterone, nandrolone, stanozolol, and trenbolone.
The physical consequences of non-medical steroid use are extensive and sometimes irreversible. In men, abuse can cause testicle shrinkage, reduced sperm count, breast tissue enlargement, and increased prostate cancer risk. In women, effects include deepening of the voice, increased facial and body hair, male-pattern baldness, and menstrual irregularities. In adolescents, steroids can permanently stunt height. Both sexes face elevated cholesterol, increasing the risk of heart attacks and strokes. Oral steroids are particularly damaging to the liver, and people who inject steroids risk contracting HIV, hepatitis B or C, and bacterial infections including a potentially fatal inflammation of the heart lining.
Misuse vs. Abuse
These two terms are sometimes used interchangeably, but clinically they describe different behaviors. Misuse refers to using a medication for a legitimate medical purpose but in an inappropriate way: taking more than prescribed, using someone else’s prescription, or crushing a pill that’s meant to be swallowed whole. Abuse, by contrast, means taking a substance specifically to get high or achieve some other non-medical psychological effect, even once.
Clinicians now generally use the term “substance use disorder” rather than “abuse” or “addiction.” It’s diagnosed on a spectrum. Meeting two or three of eleven criteria (like repeatedly using more than intended, craving the substance, or needing higher doses to get the same effect) indicates a mild disorder. Four or five criteria suggest moderate severity, and six or more point to a severe substance use disorder. The criteria cover four broad areas: losing control over use, social problems caused by use, continuing use in risky or harmful situations, and developing tolerance or withdrawal symptoms.
Cannabis
Marijuana remains the most commonly used illicit drug in the United States. In 2024, 64.2 million people aged 12 or older used it in the past year, representing 22.3% of that population. While legalization in many states has changed its legal status, cannabis use disorder is a recognized condition. Regular heavy use can lead to tolerance, withdrawal symptoms like irritability and sleep disruption, and difficulty cutting back despite wanting to. High-potency concentrates and edibles have made it easier to consume large doses, increasing the risk of dependence for frequent users.