Cannabis
Learn more about cannabis, the most used illicit drug.
Overview
Common Nicknames
Marijuana, weed, skunk or hash
Drug Class
Cannabinoid
Drug Form
Dried flower, joints, drinks, oils, tinctures, baked goods, vaporisers, lotions
Route of Administration
Smoking, eating/drinking, vaporising, directly applied to the skin
What is the science of Cannabis?
Cannabis affects the body and brain primarily through its active compounds, called cannabinoids. There are more than 100 cannabinoids identified each with their own pharmacology and properties. These compounds interact with the body's endocannabinoid system, which helps regulate many functions like mood, appetite, pain, memory, and sleep. The specific effects depend on the balance of these compounds, the method of consumption, and the individual’s unique body chemistry.
THC is the main psychoactive compound in cannabis, and it's responsible for the "high" people feel. It binds to cannabinoid receptors in the brain, particularly the CB1 receptors, which are involved in mood, memory, and coordination. This interaction can cause feelings of euphoria, altered perception, and impaired coordination. CBD, on the other hand, is non-psychoactive and has calming effects. It interacts with other receptors in the body, like CB2 receptors, which are more involved in immune function and inflammation. CBD may help reduce anxiety, pain, and inflammation without causing a "high."
Read more about the endocannabinoid system here.
Physiologically, cannabis temporarily increases blood pressure and resting heart rate.
What are the risks?
While cannabis is generally considered less harmful than most other drugs and there have been no reported deaths directly attributed to cannabis use, it’s still important to understand the potential risks.
The harm caused by cannabis use can vary widely depending on factors like the person’s age, how often they use it, the method of consumption, and the potency of the cannabis (specifically its THC and CBD content). For some people, occasional use may have minimal effects, while for others, especially heavy or long-term use, can lead to issues like memory problems, anxiety, or dependence. Cannabis dependence, though less common than with other substances, is still possible and can affect a person’s ability to stop using it even if it starts interfering with their daily life.
The only way to completely eliminate the risks of cannabis is to avoid it altogether. However, for those who choose to use it and accept the potential risks, there are many important decisions that can help minimize harm. Key choices include what type of cannabis to use, when to use it, and how to consume it.
An analysis by Drug Science in 2010 in the UK added up and compared the harm caused by 20 different drugs, and placed cannabis roughly in the middle; it causes more harm to society than several other illegal drugs (mostly because there are many more users- cannabis is the most used illegal drug in the UK) but less harm to its users than tobacco and alcohol, both of which have a higher potential to cause serious illness and death but remain legal. Another study by Drug Science looked at how changing governmental legislation on cannabis can reduce harm to users and found that state control of cannabis was the best policy to minimise drug harms.
How might the drug make you feel?
Some common effects:
Euphoria or "high": This is the most well-known effect, caused by THC, which can make users feel happy, relaxed, or even giggly.
Altered perception: Cannabis can change how users experience time, colours, and sounds, making them seem more intense or pleasurable.
Increased appetite: Often called the "munchies," cannabis can make you feel very hungry.
Relaxation or drowsiness: Many people feel calm or sleepy, especially when using strains with higher levels of CBD.
Impaired coordination and memory: Cannabis can affect motor skills, making tasks like driving or operating machinery dangerous, and it can temporarily impair memory and concentration. More information about driving can be found here.
Possible negative effects:
Anxiety or paranoia: In some people, especially with higher doses of THC, cannabis can cause feelings of nervousness, paranoia, or fear.
Visual and auditory hallucinations: Very high doses or potent strains can lead to mild visual or auditory hallucinations.
Increased heart rate: Cannabis can cause a temporary rise in heart rate and blood pressure, which might be risky for people with heart problems but otherwise harmless and short-lived.
Dry mouth and red (itchy) eyes: These are common side effects, but they’re harmless. Can easily be avoided by drinking plenty of water and using eye drops.
Nausea/Dizziness (‘whitey’): feeling faint, dizzy, nauseous, sweaty, or lightheaded, and in some cases, vomiting. This can happen after consuming too much or mixing with alcohol but it passes with time and resting.
Mixing cannabis with other drugs makes the likelihood of a negative experience greater, particularly if mixed with alcohol
Is Cannabis addictive, and what are the long-term effects?
Cannabis can be addictive for some people, though it’s generally considered less addictive than substances like nicotine, alcohol, or opioids. About 9-10% of people who use cannabis will develop cannabis use disorder (CUD), which means they become dependent on the drug and find it difficult to stop using it, even if it’s negatively affecting their lives. The risk of addiction is higher for those who start using cannabis at a young age, use it regularly, or have a history of mental health issues. Symptoms of cannabis addiction can include cravings, spending a lot of time using cannabis or recovering from its effects, and continuing to use it despite knowing it’s causing problems, such as issues with work, school, or relationships. While not everyone who uses cannabis will become addicted, it’s still important to be mindful of how often and how much you use.
Research suggests that behavioural interventions, such as cognitive behavioural therapy (CBT), motivational enhancement therapy (MET), and contingency management, can be effective in treating cannabis use disorder. You can learn more about behavioural treatments for substance use disorders on the National Institute of Mental Health website. While there are currently no FDA-approved medications specifically for treating cannabis use disorder or for medically assisted withdrawal, research into potential treatments is ongoing.
Higher concentrations of THC have been linked to an increased risk of cannabis use developing into cannabis use disorder, as well as other health issues.
The long-term effects of cannabis use can vary depending on factors such as how often it's used, the age of the user, and whether it's consumed in moderation or heavily. Some potential long-term effects may include:
Memory and learning issues: Frequent use, especially at a young age, may impact cognitive function and memory.
Risk of dependence: About 1 in 10 users may develop cannabis use disorder (CUD), where they feel the need to keep using cannabis even if it negatively impacts their life.
Respiratory issues: Smoking cannabis can damage the lungs and lead to chronic coughing or other breathing problems, particularly for tobacco-based joints.
Cannabinoid hyperemesis syndrome (CHS): rare condition caused by regular (daily) and long-term use of cannabis. The syndrome is characterised by repeated and severe bouts of vomiting. CHS only resolves when a person stops using cannabis completely. Read more here.
Not everyone will experience these effects, and some people may use cannabis regularly without significant long-term consequences. However, the risks increase with heavy, chronic use, particularly if started at a young age.
Harm Reduction and Drug-Drug Interactions
The best advice is to start low and take it slow so you can get a feel for the strength of the cannabis.
If possible, avoid smoking cannabis, as it can harm your lungs. Consider using a vaporizer or making edibles instead.
It’s best to avoid mixing cannabis with tobacco, as this not only increases the harm to your lungs but also makes cannabis more addictive, since your brain starts to link the two substances.
When using edibles, keep in mind that the effects take longer to kick in, so be patient and resist the urge to take more. Even experienced users can be caught off guard by the strength of edibles.
If you start feeling demotivated, anxious, or paranoid after using cannabis, it’s a good idea to stop. These feelings are likely to worsen if you keep using it.
Never drive after consuming cannabis. Always find a safe alternative to get around.
As with all drugs, mixing can be dangerous and should be avoided. Please check out the Drug Combinations chart & website.
Medical Uses
Cannabis has been used as medicine for thousands of years, but after the United States began its campaign against it in 1937, it was removed from medical references and pharmacopeias around the world.
There is evidence that cannabis can be effective in treating some forms of pain, and there is emerging evidence that it may have additional therapeutic uses. Research will continue to explore potential therapeutic effects of cannabis to help inform individual and public health decisions, including strategies to minimize potential harms associated with cannabis use.
In the UK, medical cannabis has been legal since 2018 and there are three licensed medicines that can be prescribed for specific conditions (Sativex, Epidyolex and Nabilone). But even at the time of writing (November 2024), medical cannabis on the NHS is extremely difficult to access and is limited to a restricted number of severe and treatment-resistant conditions, such as rare forms of epilepsy and multiple sclerosis. Estimations suggest just a handful of patients in the UK have accessed medical cannabis on the NHS. However, private clinics where patients pay for medical cannabis prescriptions are becoming increasingly popular across the UK to help provide patients with the medicine, they need but are unable to access on the NHS. It is estimated thousands of patients attend these clinics each year. These clinics can provide unlicensed medical cannabis for a variety of health conditions, but patients must pay costly bills for this.
Learn more about your rights as a medical cannabis patient here and about self-medicating with cannabis here.
Myths and Misconceptions
Cannabis is a ‘gateway’ drug
Cannabis products, along with alcohol and tobacco, are typically some of the first substances a person will come across in life, and many people who use substances start with these before trying others. However, the idea that cannabis inevitably leads to the use of harder drugs is not supported by evidence. While some people who use cannabis may go on to try other substances, cannabis itself does not directly cause this. Factors like environment, social influences, and personal circumstances play a bigger role in whether someone tries other substances.
Cannabis use causes psychosis
The relationship between cannabis and psychosis is complex and depends on several factors, including genetic predisposition, the amount and potency of cannabis consumed (high-potency cannabis carries a greater risk for psychosis compared to weaker types), early or heavy use and underlying mental health conditions. While cannabis use does not directly cause psychosis in everyone, it can increase the risk of psychotic episodes, especially in vulnerable individuals. For those with a family history of mental illness or existing mental health conditions, it’s advisable to avoid or limit cannabis use.
There's a possibility that cannabis use, especially in large amounts, could increase the likelihood of experiencing psychosis. However, since psychosis is relatively rare, it's difficult to definitively link it to cannabis use.
Legality
In the UK, cannabis is classified as a Class B drug under the Misuse of Drugs Act 1971, meaning it is illegal to possess, supply, or produce it. The law states that if caught with cannabis, you could face up to 5 years in prison, an unlimited fine, or both. However, in practice, first-time offenders are often given a cannabis warning by police, and subsequent offenses may lead to fines, arrest, or more serious penalties. Growing or selling cannabis carries harsher legal consequences, with significant penalties for anyone caught producing or distributing it, including sharing with friends, which is also considered supplying by law. Having a criminal record for cannabis-related offenses can lead to difficulties in securing employment, traveling (especially to countries like the U.S.), and could impact future opportunities, such as holding public office.
However, medical cannabis has been legal in the UK since 2018, if prescribed by a specialist for certain health problems. To be eligible for medical cannabis, you need to have a diagnosed physical or mental health condition that has not been relieved by traditional therapies. Learn more about eligibility for medical cannabis here.