Using cannabis frequently (daily or almost daily) and over a long time (several months or years) can:
Using cannabis frequently can lead to a pattern of problematic use or use disorder. This can result in dependence or addiction.
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Experiencing a cannabis addiction can cause serious harm to your:
Starting as a teen, consuming frequently (daily or near daily) and over a long time (several months or years) increases the risk of mental health problems. These problems include dependence and disorders related to anxiety and depression. Footnote 11
Quitting is not always easy. If you are struggling with your cannabis use, you can:
Cannabis has not been linked to birth defects, but research suggests that using cannabis regularly during pregnancy could affect a baby's brain development as they get older.
Read the latest updates on cannabis, cannabinoids and cancer – the evidence so far on the Cancer Research UK website.
Cannabis also increases the risk of a relapse in people who already have schizophrenia, and it can make psychotic symptoms worse.
Other risks of cannabis
Regularly smoking cannabis with tobacco increases the risk of a baby being born small or premature.
The risk of developing a psychotic illness is higher in people who:
Some examples include:
A psychotic illness is one where you have hallucinations (seeing things that are not really there) and delusions (believing things that are not really true).
Relying on marijuana alone as treatment or for managing side effects while avoiding or delaying conventional medical care for cancer may have serious health consequences. 2
The impact depends on many factors and is different for each person. It also depends on the amount of tetrahydrocannabinol (THC) in marijuana (i.e., marijuana 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.
Marijuana and cannabinoids (the active chemicals in marijuana that cause drug-like effects throughout the body, including the central nervous system and the immune system). The main active cannabinoid in marijuana 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 marijuana and cannabinoids have been studied with respect to managing side effects of cancer and cancer therapies, there are no ongoing clinical trials of marijuana or cannabinoids in treating cancer in people. 9 Studies so far have not shown that cannabinoids help control or cure the disease. 2 And like many other drugs, marijuana can cause side effects and complications.
Developing brains, like those in babies, children, and teenagers are especially susceptible to the hurtful effects of marijuana. Although scientists are still learning about these effects of marijuana on the developing brain, studies show that marijuana use by mothers during pregnancy may be linked to problems with attention, memory, problem-solving skills, and behavior problems in their children. 3-7
Marijuana’s effects on these abilities may last a long time or even be permanent. This means that someone who uses marijuana may not do as well in school and may have trouble remembering things. 1-3