Updated: 31 January 2023 & medically reviewed by Dr. Samantha Miller
Marijuana, also known as weed, is the most commonly abused substance after tobacco and alcohol. In 2018, more than 11.8 million young adults reported marijuana use in the previous year.
- Studies have shown that marijuana may affect brain development. Those who begin smoking marijuana in their teens and continue to abuse the drug over an extended period may develop impaired memory, learning functions, and cognitive ability
- Marijuana concentrates contain extraordinarily high THC levels that could range from 40 to 80 percent. This form of marijuana can be up to four times higher in THC content than high grade or top-shelf marijuana, which normally measures around 20 percent THC levels
- While marijuana is a widely used and addictive substance, there has been much debate in recent years as to its value as a medicinal property. Between 1996 and 2020, 36 states and four Territories passed comprehensive medical marijuana and cannabis programs
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Marijuana, also known as weed, herb, pot, grass, bud, ganja, Mary Jane, and a vast number of other slang terms, is a greenish-gray mixture of the dried flowers of Cannabis sativa. Some people smoke marijuana in hand-rolled cigarettes called joints, pipes, water pipes (sometimes called bongs), or blunts (marijuana rolled in cigar wraps).
People also use marijuana to brew teas and is frequently mixed into foods (edibles) such as brownies. Consuming marijuana through vaporizers has also become increasingly popular. Stronger forms of marijuana include sinsemilla (from specially tended female plants) and concentrated resins containing high doses of marijuana's active ingredients, including honey like hash oil, waxy budder, and hard amberlike shatter.
The main psychoactive (mind-altering) chemical in marijuana is delta-9-tetrahydrocannabinol (THC). The chemical is found in resin produced by the leaves and buds, primarily of the female cannabis plant. The plant also contains more than 500 other chemicals, including more than 100 compounds that are chemically related to THC, called cannabinoids. 
There is also an emerging trend for synthetic marijuana, often referred to as spice or K2. This artificial form of the drug can be far more dangerous as it contains unregulated chemicals. Read here to learn more about the risks of spice abuse.
What are marijuana concentrates?
A marijuana concentrate is a highly potent concentrated form of THC (tetrahydrocannabinol) that is most similar in appearance to either honey or butter, and commonly referred to or known on the street as 'honey oil' or 'budder'.
A form of cannabis concentrate that has gained popularity in recent years is "shatter", an incredibly potent form of the drug that often contains over 60% pure THC. Read our guide on shatter to learn more about this potent cannabis concentrate.
What are marijuana concentrates origins?
Marijuana concentrates contain extraordinarily high THC levels that could range from 40 to 80 percent. This form of marijuana can be up to four times higher in THC content than high grade or top-shelf marijuana, which normally measures around 20 percent THC levels. Many methods are utilized to convert or "manufacture" marijuana into marijuana concentrates. One method is the butane extraction process. This process is particularly dangerous because it uses highly flammable butane to extract the THC from the cannabis plant.
What do marijuana concentrates look like?
Marijuana concentrates are similar in appearance to honey or butter and are either brown or gold in color.
How are marijuana concentrates used?
Marijuana concentrates can be mixed with various food or drink products to be consumed orally; however, smoking remains the most popular route of administration by use of water or oil pipes. A disturbing aspect of this emerging threat is the inhalation of concentrates via electronic cigarettes (also known as e-cigarettes) or vaporizers.
Many marijuana concentrate users prefer the e-cigarette/vaporizer because it is smokeless, sometimes odorless, and easy to hide or conceal. The user takes a small amount of marijuana concentrate, referred to as a "dab," then heats the substance using the e-cigarette/vaporizer, producing vapors that ensure an instant "high" effect upon the user. Using an e-cigarette/ vaporizer to inhale marijuana concentrates is commonly referred to as "dabbing" or "vaping".
How long does marijuana stay in your system?
Infrequent users who smoke marijuana less than twice a week can test positive for 1-3 days from the last time they took it. A moderate user, several times per week, can test positive for 7-21 days after their previous use. A heavy user can test positive for a month or longer after last use. People who ingest marijuana (edibles) may produce a positive result for 1-5 days.
Street names for marijuana
Marijuana goes by many street or slang names, some are intended as fun nicknames while others are used to deceive law enforcement. Marijuana street names are derived from the substance's appearance, origin, and effect. Some of the most common marijuana street names include:
- Mary Jane
- Aunt Mary
- Texas tea
- Red bud
- Indian hemp
- Laughing grass
- Magic smoke
What is medical marijuana?
While marijuana is a widely used and addictive substance, there has been much debate in recent years as to its value as a medicinal property. Between 1996 and 2020, 36 states and four Territories passed comprehensive medical marijuana and cannabis programs. In those areas, doctors may prescribe marijuana for patients who may benefit from its use. 
Marijuana is occasionally used to treat the following:
HIV and AIDS
Lou Gehrig's Disease
While Marijuana has yet to be approved as an official medicine, the U.S Food and Drug Administration has approved a few varieties of pill cannabinoids.
According to a study by the National Academies of Sciences, Engineering, and Medicine, THC and cannabinoid drugs' potential therapeutic benefits include:
Improving muscle spasms, stiffness, and fatigue in multiple sclerosis patients.
The same study notes that there are also potential benefits to smoking marijuana, such as reduced anxiety and sedation. However, these effects may be deemed undesirable for all patients. 
In most states that allow medicinal marijuana, there are strict laws under which a doctor may prescribe it. In most cases, the patient will need to have a marijuana registration or ID card that allows them to pick up a prescription and can also be used if stopped by police while intoxicated.
Short-term effects of marijuana abuse
When inhaling marijuana smoke, THC passes through the lungs and enters the bloodstream quickly. The chemical is carried through the blood to the brain, where it acts on specific brain cell receptors and over-activates them, creating the 'high' felt from marijuana. If marijuana is taken orally, this reaction is slower, often taking effect around 30 minutes to 1 hour after taking.
In addition to the high felt, people who take marijuana often experience some of these effects:
altered senses (for example, seeing brighter colors)
altered sense of time
changes in mood
impaired body movement
difficulty with thinking and problem-solving
hallucinations (when taken in high doses)
delusions (when taken in high doses)
psychosis (risk is highest with regular use of high potency marijuana) 
Long-term effects of marijuana abuse
Studies have shown that marijuana may affect brain development. Those who begin smoking marijuana in their teens and continue to abuse the drug over an extended period may develop impaired memory, learning functions, and cognitive ability. This is due to connections in the brain that relate to these functions not being able to form. Research is still ongoing as to the exact extent of this impairment and whether it is permanent.
For example, a study from New Zealand conducted in part by researchers at Duke University showed that people who started smoking marijuana heavily in their teens and had an ongoing marijuana use disorder lost an average of 8 IQ points between ages 13 and 38. The lost mental abilities didn't fully return in those who quit marijuana as adults. Those who started smoking weed as adults didn't show notable IQ declines.
In another recent study on twins, those who used marijuana showed a significant decline in general knowledge and verbal ability (equivalent to 4 IQ points) between preteen and early adulthood. However, no predictable difference was found between twins when one used marijuana, and the other didn't. This suggests that the IQ decline in marijuana users may be caused by something other than marijuana, such as shared familial factors (e.g., genetics, family environment).
Is marijuana addictive?
When a person uses marijuana, the cannabinoid receptor in the brain is activated by a neurotransmitter called Anandamide. However, the THC component of marijuana blocks neurotransmitters like Anandamide and can cause the body to be incapable of producing sufficient levels on its own. This can lead to marijuana abusers developing a dependence on the drug, requiring it to feel the same sensation or feel normal.
Marijuana abuse can often lead to someone developing an addiction, though they are not the same thing. Marijuana abuse will often cause harmful side effects to the user, but this does not mean they cannot quit on their own. Marijuana addiction is more complicated and often requires help to overcome.
Like most forms of addiction, a person with a marijuana use disorder will be diagnosed by a licensed professional using these 11 criteria, outlined by the DSM-5:
Hazardous use: You have used the substance in ways that are dangerous to yourself and/or others, i.e., overdosed, driven while under the influence, or blacked out.
Social or interpersonal problems related to use: Substance use has caused relationship problems or conflicts with others.
Neglected major roles to use: You have failed to meet your responsibilities at work, school, or home because of substance use.
Withdrawal: When you stop using the substance, you experience withdrawal symptoms.
Tolerance: You have built up a tolerance to the substance so that you have to use more to get the same effect.
Used larger amounts/longer: You have started to use larger amounts or use the substance for longer amounts of time.
Repeated attempts to control the use or quit: You've tried to cut back or quit entirely but haven't been successful.
Much time spent using: You spend a lot of your time using the substance.
Physical or psychological problems related to use: Your substance use has led to physical health problems, such as liver damage or lung cancer, or psychological issues, such as depression or anxiety.
Activities are given up in order to use: You have skipped activities or stopped doing activities you once enjoyed in order to use the substance.
Craving: You have experienced cravings for the substance.
These criteria are measured by the substance's negative impact on a person's life, including physical, psychological, and behavioral measures, classified as mild, moderate, and severe. The criteria are measured against the previous 12 months of substance use, and a score of 2-3 is considered mild, 3-5 moderate, and six or more severe. Even severe marijuana addictions can be treated and overcome.
Visit here for more information and guides about the effects of marijuana abuse.
Marijuana withdrawal symptoms
As attitudes continue to change towards marijuana use, either through its legal status or its medicinal qualities, the growing perception is that marijuana use is not harmful or addictive. In actuality, marijuana abuse can lead to addiction, and trying to stop once a dependence or addiction has formed can lead to marijuana withdrawal symptoms.
According to the Centers for Disease Control and Prevention (CDC), 1 in 10 Americans who use cannabis will become addicted. That number jumps to 1 in 6 if you begin using marijuana before the age of 18.
Occasional cannabis abuse may not cause withdrawal symptoms if use stops. However, for those who abuse marijuana regularly, stopping can cause withdrawal symptoms such as mood swings, disturbed sleep, and irritability, though there may be additional symptoms also.
Symptoms of withdrawal
Symptoms of marijuana withdrawal may include:
sleep difficulties, including insomnia
loss of focus
cravings for marijuana
sweating, including cold sweats
increased feelings of depression
stomach problems 
These symptoms may not be dangerous but can cause discomfort and unrest. They will also appear differently from person to person, ranging from mild to severe, but the more prolonged marijuana abuse continues, the greater the likelihood of withdrawal symptoms.
Treating a marijuana addiction
Those who have been using marijuana over an extended period or in high doses may find it hard to stop independently. As with all forms of substance abuse, the best way to stop is by getting help. Inpatient rehab, outpatient treatment centers, an addiction treatment program, therapy, and support groups are just some ways people suffering from marijuana dependence or addiction can stop using through professional support. If you or someone you know is suffering from a marijuana use disorder, contact a treatment center today to get help. 
These are some of the top questions asked about marijuana:
How much does marijuana cost?
Marijuana costs vary from state to state and can depend on whether the drug is available legally or not. Read our guide to find out more about the street cost of marijuana.
Is marijuana legal in the US?
Increased marijuana use both medically and recreationally has led many states to relax laws around weed consumption. However, there are still those who uphold strict marijuana laws that carry heavy penalties. Click here to check our full list of states where marijuana is legal.
Does marijuana kill brain cells?
Some studies of marijuana abuse in adolescence indicate that there is a decline in IQ if abuse continues into adulthood. Read here to find out more about marijuana's effect on the brain.