Marijuana (cannabis) refers to the dried leaves, flowers, stems, and seeds from the Cannabis sativa or Cannabis indica plant and is the most commonly used illicit substance. It is now legal in some states for medical and recreational use. Some people use marijuana for its pleasurable high, but this drug also impairs short-term memory and learning, the ability to focus, and coordination. It also increases heart rate, can harm the lungs, and can increase the risk of psychosis in vulnerable people. Data suggest that 30 percent of those who use marijuana may have some degree of marijuana use disorder.7 People who begin using marijuana before the age of 18 are four to seven times more likely than adults to develop a marijuana use disorder.8 For more information, visit www.drugabuse.gov/drugs-abuse/marijuana.
Marijuana Research at NIDA and NIH
As part of its mandate to study drug use and addiction and other health effects of both legal and illegal drugs, NIDA funds a wide range of research on marijuana; its main mind-altering ingredient, THC; and other chemicals, such as cannabidiol (CBD). For more information about NIDA research on marijuana and cannabinoids, visit drugabuse.gov/drugs-abuse/marijuana/marijuana-research-nida. NIDA is one of 27 institutes and centers who could fund research on marijuana. For more information about NIH-funded research on marijuana, visit www.drugabuse.gov/drugs-abuse/marijuana/nih-research-marijuana-cannabinoids.
Although many states have legalized marijuana for medical use, the scientific evidence to date is not sufficient for it to gain U.S. Food and Drug Administration (FDA) approval, for two main reasons.
First, there have not been enough clinical trials showing that marijuana’s benefits outweigh its health risks. The FDA requires carefully conducted studies (clinical trials) in hundreds to thousands of patients to determine benefits and risks.
Second, to be considered a legitimate medicine, a substance must have well-defined and measurable ingredients that are consistent from one unit to the next (such as a pill or injection). This consistency allows doctors to determine the dose and frequency. As the marijuana plant contains hundreds of chemical compounds that may have different effects and that vary from plant to plant, evaluating the whole plant as a medicine is difficult.
However, synthetic THC-based drugs to treat nausea caused by chemotherapy and increase appetite in patients with extreme weight loss caused by AIDS are already FDA-approved and prescribed. In addition, the FDA recently approved Epidiolex®, the first medicine derived from the marijuana plant itself. Epidiolex® is made using CBD, a non-pscyhoactive ingredient in the plant, and has shown efficacy in treating two rare and severe forms of epilepsy in children. For more information, see our Marijuana as Medicine DrugFacts at drugabuse.gov/publications/drugfacts/marijuana-medicine.
Synthetic Cannabinoids (K2/Spice)
Synthetic cannabinoids are human-made, mind-altering chemicals that are either sprayed on dried, shredded plant material so they can be smoked (herbal incense) or sold as liquids to be vaporized and inhaled in e-cigarettes and other devices (liquid incense) to produce a high.
These chemicals are called cannabinoids because they are related to chemicals found in the marijuana plant. Because of this similarity, synthetic cannabinoids are sometimes misleadingly called "synthetic marijuana" (or "fake weed"), and they are often marketed as "safe," legal alternatives to that drug. In fact, they are not safe and may affect the brain more powerfully and differently than marijuana; their actual effects can be unpredictable and, in some cases, severe or even life-threatening.
Synthetic cannabinoids are part of a group of drugs called new psychoactive substances (NPS). These are unregulated mind-altering substances that have become recently available on the market and are intended to produce the same effects as illegal drugs. Some of these substances may have been around for years but have reentered the market in altered chemical forms, or due to renewed popularity.
People taken to the emergency room after using synthetic cannabinoids report rapid heart rate, vomiting, violent behavior, and suicidal thoughts. These drugs can also raise blood pressure and reduce blood supply to the heart, as well as cause kidney damage and seizures. Synthetic cannabinoids have a high addictive potential and no medical benefit, so the U.S. Drug Enforcement Administration (DEA) has made it illegal to sell, buy, or possess them. However, manufacturers try to sidestep these laws by changing the chemical formulas in their mixtures. For more information, visit drugabuse.gov/drugs-abuse/synthetic-cannabinoids-k2spice.
Prescription and Over-the-Counter Medications
Some prescription and over-the-counter medications are increasingly being misused (used in ways other than intended or without a prescription). This practice can lead to addiction and, in some cases, overdose. Among the most disturbing aspects of this emerging trend is its prevalence among teenagers and young adults, as well as the common misperception that because these are used medically or prescribed by physicians, they are safe even when not used as intended. Commonly misused classes of prescription drugs include opioid pain relievers, stimulants, and central nervous system (CNS) depressants (sedatives and tranquilizers).
Opioids are a class of drugs naturally found in the opium poppy plant. Some prescription opioids are made from the plant directly, and others are made by scientists in labs using the same chemical structure. Opioids are often used as medicines because they contain chemicals that relax the body and can relieve pain. Prescription opioids are used mostly to treat moderate to severe pain, though some opioids can be used to treat coughing and diarrhea. Opioids can also make people feel very relaxed and high—which is why they are sometimes used for non-medical reasons. This can be dangerous because opioids can be highly addictive, and overdoses and death are common. Heroin is one of the world’s most dangerous opioids, and is never used as a medicine in the United States. Prescription opioids and heroin are chemically similar and can produce a similar high. In some places, heroin is cheaper and easier to get than prescription opioids, so some people switch to using heroin instead.
In the short term, opioids can relieve pain and make people feel relaxed and happy. However, opioids can also cause drowsiness, confusion, nausea, constipation, euphoria, and slowed breathing. Slowed breathing can cause hypoxia, a condition that results when too little oxygen reaches the brain. Hypoxia can have short- and long-term psychological and neurological effects, including coma, permanent brain damage, or death, resulting in increasingly higher overdose deaths in the U.S. Researchers are also investigating the long-term effects of opioid addiction on the brain, including whether damage can be reversed.
Stimulants such as Methylphenidate (Ritalin®, Concerta®) and amphetamines (Adderall®, Dexedrine®) are commonly prescribed for attention-deficit hyperactivity disorder (ADHD) and narcolepsy—uncontrollable episodes of deep sleep. Prescription stimulants increase alertness, attention, and energy. Stimulants enhance the effects of certain neurotransmitters in the brain, such as norepinephrine and dopamine. Dopamine affects feelings of pleasure. Norepinephrine affects blood vessels, blood pressure and heart rate, blood sugar, and breathing. People who use prescription stimulants report feeling a "rush" (euphoria) along with increased blood pressure and heart rate, increased breathing, decreased blood flow, increased blood sugar, opened-up breathing passages. At high doses, prescription stimulants can lead to a dangerously high body temperature, an irregular heartbeat, heart failure, and seizures. Repeated misuse of prescription stimulants, even within a short period, can cause psychosis, anger, or paranoia.
CNS Depressants are medicines that include sedatives, tranquilizers, and hypnotics. They are usually prescribed to treat anxiety, panic, acute stress reactions, and sleep disorders. Sedatives primarily include barbiturates (e.g., phenobarbitol) but also include sleep medications such as Ambien® and Lunesta®. Tranquilizers primarily include benzodiazepines, such as Valium® and Xanax®, but also include muscle relaxants and other anti-anxiety medications. These medications slow brain activity, which can cause drowsiness, slurred speech, poor concentration, confusion, dizziness, problems with movement and memory, lowered blood pressure, and slowed breathing, especially when misused.
Over-the-counter medicines that are commonly misused include dextromethorphan (DXM), a cough suppressant, and loperamide, an antidiarrheal. Products containing DXM can be sold as cough syrups, gel capsules, and pills that can look like candies. They are often misused by young people, who refer to the practice as "robotripping" or "skittling." Loperamide is available in tablet, capsule, or liquid form. Both DXM and loperamide are opioids. DXM does not have effects on pain reduction or addiction and does not act on the opioid receptors. However, when taken in large doses, DXM can cause a depressant and hallucinogenic effect. Short-term effects of DXM misuse can range from mild stimulation to alcohol- or marijuana-like intoxication. Loperamide does not enter the brain; but when taken in large doses and combined with other substances, it may cause the drug to act in a similar way to other opioids. Loperamide misuse can cause euphoria, similar to other opioids, or lessen cravings and withdrawal symptoms, but other effects have not been well studied and reports are mixed.
For more information about misuse of prescription and over-the-counter medicines, view the following NIDA resources: