About 1 in 10 marihuana users will become addicted. For people who begin using before the age of 18, that number rises to 1 in 6.
Some of the signs that someone might be addicted include:
People who are addicted to marihuana may also be at a higher risk of other negative consequences of using the drug, such as problems with attention, memory, and learning. Some people who are addicted need to smoke more and more marihuana to get the same high. It is also important to be aware that the amount of tetrahydrocannabinol (THC) in marihuana (i.e., marihuana potency or strength) has increased over the past few decades. The higher the THC content, the stronger the effects on the brain. In addition, some methods of using marihuana (e.g., dabbing, edibles) may deliver very high levels of THC to the user.5 Researchers do not yet know the full extent of the consequences when the body and brain (especially the developing brain) are exposed to high concentrations of THC or how recent increases in potency affect the risk of someone becoming addicted.
Marihuana use directly affects the brain — specifically the parts of the brain responsible for memory, learning, attention, decision making, coordination, emotions, and reaction time.
Heavy users of marihuana can have short-term problems with attention, memory, and learning, which can affect relationships and mood.
Marihuana also affects brain development. When marihuana users begin using as teenagers, the drug may reduce attention, memory, and learning functions and affect how the brain builds connections between the areas necessary for these functions.
Marihuana’s effects on these abilities may last a long time or even be permanent. This means that someone who uses marihuana may not do as well in school and may have trouble remembering things.
The impact depends on many factors and is different for each person. It also depends on the amount of tetrahydrocannabinol (THC) in marihuana (i.e., marihuana potency or strength), how often it is used, the age of first use, and whether other substances (e.g., tobacco and alcohol) are used at the same time.
Developing brains, like those in babies, children, and teenagers are especially susceptible to the hurtful effects of marihuana. Although scientists are still learning about these effects of marihuana on the developing brain, studies show that marihuana use by mothers during pregnancy may be linked to problems with attention, memory, problem-solving skills, and behavior problems in their children.
Cannabinoids are the active chemicals in marihuana that cause drug-like effects throughout the body, including the central nervous system and the immune system. The main active cannabinoid in marihuana is delta-9-THC. Another active cannabinoid is cannabidiol (CBD), which may relieve pain and lower inflammation without causing the “high” of delta-9-THC. Although marihuana and cannabinoids have been studied with respect to managing side effects of cancer and cancer therapies, there are no ongoing clinical trials of marihuana or cannabinoids in treating cancer in people. Studies so far have not shown that cannabinoids help control or cure the disease. And like many other drugs, marihuana can cause side effects and complications.
Relying on marihuana alone as treatment or for managing side effects while avoiding or delaying conventional medical care for cancer may have serious health consequences.
Studies of man-made forms of the chemicals found in the marihuana plant can be helpful in treating nausea and vomiting from cancer chemotherapy. Studies have found that marihuana can be helpful in treating neuropathic pain (pain caused by damaged nerves).
At this time, there is not enough evidence to recommend that patients inhale or ingest marihuana as a treatment for cancer-related symptoms or side effects of cancer therapy.
Smoked marihuana delivers THC and other cannabinoids to the body, but it also delivers harmful substances to users and those close by, including many of the same substances found in tobacco smoke, which are harmful to the lungs and cardiovascular system.
Researchers have found limited evidence of an association between current, frequent, or chronic marihuana smoking and testicular cancer (non-seminoma-type).
Because marihuana plants come in different strains with different levels of active chemicals, it can make each user’s experience very hard to predict. More research is needed to understand the full impact of marihuana use on cancer.
Even though pain management is one of the most common reasons people use medical marihuana in the U.S., there is limited evidence that marihuana works to treat most types of chronic pain.
A few studies have found that marihuana can be helpful in treating neuropathic pain (pain caused by damaged nerves). However, more research is needed to know if marihuana is any better or any worse than other options for managing chronic pain.
Using marihuana makes the heart beat faster. It could also lead to increased risk of stroke and heart disease. However, most of the scientific studies linking marihuana to heart attacks and strokes are based on reports from people who smoked it. Smoked marihuana delivers THC and other cannabinoids to the body, but it also delivers harmful substances to users and those close by, including many of the same substances found in tobacco smoke, which are harmful to the lungs and cardiovascular system. So it’s hard to separate the effects of the compounds in marihuana on the cardiovascular system from the hazards posed by the irritants and other chemicals contained in the smoke. More research is needed to understand the full impact of marihuana use on the circulatory system to determine if marihuana use leads to higher risk of death from these causes.
How marihuana affects lung health is determined by how it’s consumed. In many cases, marihuana is smoked in the form hand-rolled cigarettes (joints), in pipes or water pipes (bongs), in bowls, or in blunts—emptied cigars that have been partly or completely refilled with marihuana. Smoked marihuana, in any form, can harm lung tissues and cause scarring and damage to small blood vessels. Smoke from marihuana contains many of the same toxins, irritants, and carcinogens as tobacco smoke. Smoking marihuana can also lead to a greater risk of bronchitis, cough, and phlegm production. These symptoms generally improve when marihuana smokers quit.
The known health risks of secondhand exposure to cigarette smoke—to the heart or lungs, for instance—raise questions about whether secondhand exposure to marihuana smoke poses similar health risks. While there is very little data on the health consequences of breathing secondhand marihuana smoke, there is concern that it could cause harmful health effects, including among children.
Recent studies have found strong associations between those who said there was someone in the home who used marihuana or a caretaker who used marihuana and the child having detectable levels of THC — the psychoactive ingredient in marihuana. Children exposed to the psychoactive compounds in marihuana are potentially at risk for negative health effects, including developmental problems for babies whose mothers used marihuana while pregnant. 8Other research shows that marihuana use during adolescence can impact the developing teenage brain and cause problems with attention, motivation, and memory.
Marihuana use, especially frequent (daily or near daily) use and use in high doses, can cause disorientation, and sometimes cause unpleasant thoughts or feelings of anxiety and paranoia.
Marihuana users are significantly more likely than nonusers to develop temporary psychosis (not knowing what is real, hallucinations and paranoia) and long-lasting mental disorders, including schizophrenia (a type of mental illness where people might see or hear things that aren’t really there).
Marihuana use has also been linked to depression and anxiety, and suicide among teens. However, it is not known whether this is a causal relationship or simply an association.
Edibles, or food and drink products infused with marihuana and eaten, have some different risks than smoking marihuana, including a greater risk of poisoning. Unlike smoked marihuana, edibles can:
It is also important to remember that marihuana affects children differently than adults. Since marihuana has become legal in some states, children have accidentally eaten marihuana products that looked like candy and treats, which made them sick enough to need emergency medical care. 3
If you use marihuana products, keep them in childproof containers and out of the reach of children. For additional questions, you can contact your health care provider, your health department, the Poison Helpline at 1-800-222-1222, or 911 if it’s an emergency.
RISK OF USING OTHER DRUGS
The concept of marihuana as a “gateway drug”—where using marihuana leads a person to use other drugs—generates a lot of disagreement. Researchers haven’t found a definite answer yet. However, most people who use marihuana do not go on to use other, “harder” drugs.
It is important to remember that people of any age, sex, or economic status can become addicted to marihuana or other drugs. Things that can affect the likelihood of substance use include: