Oct 17th 2023
Cannabis – also known by a host of other names such as pot, weed, marijuana and Ganja – is a drug that comes from a plant (cannabis sativa). Cannabis use can affect our minds and bodies. Here we look at the link between cannabis and our mental and physical health.
Cannabis contains over 100 different chemicals called cannabinoids . Some examples are cannabidiol (CBD) and Tetrahydrocannabinol (THC). THC is the main active ingredient in cannabis. Potent forms of cannabis (‘skunk’) have a greater effect due to the high levels of THC.
When smoked, cannabis will go into your bloodstream and will quickly be carried to your brain. Once there it will attach to your receptors, or the nerve endings in your body which respond to certain changes and stimuli. This results in your brain releasing certain neurotransmitters and hormones, which can affect your thoughts, feelings and behaviors . Levels of dopamine - a neurotransmitter which plays an important role in pleasure and reward  – are thought to be affected by cannabis use. 
Cannabis can also be eaten – for example, baked into brownies or bought in the form of chocolate or gummy bears. When ‘edibles’ are consumed, cannabis will take longer to get into your bloodstream, travelling through your stomach and liver first. However, its effects are often more pronounced and last longer. Because edibles take longer to have an effect, and it’s more difficult to know the dosage of THC you’re consuming, it’s important to ‘start low and go slow’ if you decide to use cannabis in this way. 
Cannabis has both short and long term effects on our brains.
Recent marijuana use (within 24 hours) has an immediate impact on thinking, attention, memory, coordination, movement and time perception. 
Longer term, it is thought that developing brains in infants, young people, and adolescents are especially susceptible to the harmful effects of cannabis and THC.  Various pieces of research have linked cannabis use in expectant mothers with problems with attention, memory, problem-solving skills, and behavior in their children after birth. .
Using cannabis before the age 18 may affect how the brain builds connections for functions like attention, memory, and learning. These effects could last a long time, or even be permanent . More research is needed to fully understand the implications of cannabis use in young people.
The impact of cannabis on the brain depends on many factors, including:
Cannabis is now legal in most US states for recreational or medicinal use, including alleviating nausea and sickness in chemotherapy patients.  However, cannabis should not be perceived as ‘safe’ to use. It can have both positive and negative effects on our minds and bodies, and this relationship is not yet fully understood.
When people refer to ‘getting high’, they are normally talking about some of the perceived benefits of using cannabis. These could include:
Unfortunately, there are some downsides too, including some severe effects on our mental health . The negative effects of weed range from mild, such as mood changes and increased anxiety, to severe, including visual or auditory hallucinations like seeing or hearing things that others can’t. Other reported effects include:
Estimates suggest around 3 in 10 marijuana users in the US have cannabis use disorder – defined as problematic cannabis use (abuse or dependence).  You’re more likely to become addicted if you start using it before the age of 18 or use it every day. You might find you build up a tolerance to cannabis if you use it regularly, meaning you need to consume more in order to get the same effect .
Those addicted to cannabis often report experiencing withdrawal symptoms when they don’t use it. These can include changes to our feelings, thoughts, and behaviors, such as:
UK research  has found a correlation between cannabis use and prevalence of mild, moderate, and severe mental health problems, such as depression, anxiety, and serious mental illness (SMI) – a category under which conditions like schizophrenia are classified.
Using cannabis – especially at high doses - can induce a temporary psychotic episode in some individuals, meaning that they lose touch with reality . The association between cannabis use and psychosis or psychotic symptoms is possibly bidirectional. Meaning, people who use cannabis regularly are more likely to develop psychotic disorders than the general population, and experiencing psychosis increases your likelihood of using cannabis. Genetic factors could also play a role both in terms of likelihood of psychosis and cannabis use. 
Admissions data from the University of Colorado hospital in Denver  suggests that those who had ingested cannabis in the form of edibles were more likely to report heart problems and psychiatric symptoms, such as psychosis and anxiety, compared to those who had inhaled (smoked) cannabis. The study however is limited to one emergency room making it difficult to generalize to the wider population.
Although a link has been established between frequent cannabis use and mental health, the relationship is complicated, and we can’t say for certain that one causes the other. This is because people with mental health problems are more likely than the general population to use cannabis (sometimes known as ‘self-medicating’).  There are also a number of other contributory factors to poor mental health among cannabis users, including starting to use weed at an early age, using strong types of cannabis (with a high potency of THC), and the presence of any ‘genetic vulnerabilities’ (an increased risk of developing a mental health problem among those who have family members with a diagnosed mental health condition).
In addition, other factors that influence mental health—such as adverse childhood events (ACEs), trauma, and stress—also influence how likely someone is to use drugs, including cannabis. Given the multitude of factors involved, we need more research to better understand the relationship between cannabis and mental health.
Cannabis use can affect our physical health too.
If you want to cut down on your cannabis use, or quit altogether, it’s worth thinking about the reasons why you’re using cannabis, and what is making it difficult to stop.
If you’re smoking cannabis in a joint with tobacco you may become addicted to nicotine. Smoking tobacco increases your risk of associated diseases such as lung cancer, stroke, and heart disease.  It could be helpful to speak to someone about stopping smoking altogether. Nicotine is addictive so bear in mind that it can be difficult to stop. But remember, people can and do, so it’s worth persevering. Do ask for support, and don’t be disheartened if you can’t stop straight away.
Support for smoking cessation includes:
If you’re using cannabis to help manage a mental health problem or emotional difficulties, it’s important to get help for your mental health. It’s often a combination of things that work best in managing a mental health problem. Treatment may involve a combination of psychiatric medication, talk therapy, exercise, and spending time with loved ones. A good place to start is by talking to your doctor or finding a therapist through MentalHealth.com.
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