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Cannabis vs Alcohol

Alcohol as a drug, is legal in the UK, but cannabis is defined as a class B substance under the Misuse of Drugs Act 1971 making it an illegal drug.

Logically, this should indicate that cannabis is the most likely of the two to cause harm, but with 7,565 alcohol-related deaths in 2019 and only 31 loosely connected to cannabis, the reality is much more complicated.

What type of drugs are alcohol and cannabis?

Drugs can be categorised into four main types: depressants, stimulants, hallucinogens and opiates.

Alcohol is a depressant and can slow down your brain function resulting in you feeling tired and sleepy. However, it can also produce stimulant-like energising effects when taken in small amounts. Substances that can create two distinct results are known as biphasic.

Cannabis doesn't fit neatly into one category but shows characteristics of depressants, stimulants and hallucinogens:

Depressant – For some people, using THC cannabis can produce sensations of relaxation and tiredness. Different types of cannabis produce slightly altered effects; for example, strains that are dominantly descended from indica cannabis genetics usually have a more potent depressant impact than those from sativa dominant plants.

Stimulant – Stimulants increase alertness and improve mood by interacting with neurotransmitters in the brain. The stimulant effect of cannabis is a sensation of euphoria, increased heart rate and happy mood. Most types produce this to some degree, but generally, sativa strains have more energetic effects.

Hallucinogen – Hallucinogens produce psychoactive effects that alter the user's experience of reality. Although cannabis is regularly classified as hallucinogenic, studies report that these effects are rare with whole-plant cannabis and more common with THC-only preparations used during scientific research.

Opiate – Despite each being able to produce a broad range of effects, neither cannabis nor alcohol is ever classified as an opiate. Opiates interact with opiate receptors in the nervous system, activating the brain's pleasure sensors and producing depressant-like pain-relieving effects.

How does alcohol affect the body?

When you drink alcoholic beverages, the alcohol passes into your bloodstream through the wall of your stomach and small intestines. Because it's a toxin, your liver works hard to break it down before it can have any significant effects. However, on average, your liver can only detoxify about one unit per hour.

If you drink more than this, the level of alcohol travelling around your body increases before it can be broken down. This causes several effects:


  • It widens your blood vessels reducing blood pressure.
  • Small amounts may improve your mood.
  • Some studies show that moderate amounts of alcohol may protect against some conditions such as cardiovascular disease.


  • Wider blood vessels can cause your skin to flush and your core temperature to drop.
  • More significant amounts can cause feelings of depression or aggression.
  • Alcohol reduces inhibitions and causes a lack of coordination.
  • It causes intoxication, and you may slur your words or have blurred vision.
  • It's a diuretic, so you'll feel thirsty and may need to go to the toilet more often.
  • Large amounts of alcohol can result in passing out, vomiting or alcohol poisoning.
  • In the long term, regular alcohol abuse and heavy drinking can cause memory loss, high blood pressure, addiction, heart conditions, stomach ulcers and liver disease.
  • Long term, regular excessive alcohol consumption can increase your risk of stroke and cause mental health conditions, including depression and bipolar disorder.

In the UK, based on alcohol research, the NHS advises that men and women should not drink more than 14 units of alcohol per week. That's the equivalent of approximately 6 pints or ten small glasses of wine.

How does THC affect the body?

THC is the most abundant intoxicating compound found in the cannabis plant. Smoking cannabis, vaping or ingesting it, passes the THC into the bloodstream where it's transported to cells and interacts with chemical receptors. These interactions can be with the endocannabinoid or endocrine systems and produce a range of different effects. Some occur immediately, but others are only noticed after repeated long term use.


  • Interactions with signalling systems in the brain can activate the brain's pleasure centre, causing the 'high' euphoric sensations.
  • Some people use high THC cannabis strains medicinally for various reasons, including for anxiety and chronic pain conditions.
  • THC enhances sensations of taste and increases appetite.



  • Similar to alcohol, THC can lower inhibitions and may affect your judgement.
  • Large amounts of THC or prolonged use have been found to produce intense anxiety and feelings of paranoia in some people.
  • THC acts as a stimulant and increases heart rate.
  • High levels of THC can disrupt the activity in parts of your brain, making it hard to recall memories and slowing down your reaction times.

How does CBD affect the body?

Cannabidiol (CBD) is a beneficial cannabinoid. It's also found in cannabis plants but doesn't produce any intoxicating effects. It interacts with the human body in several different ways, including by blocking enzymes from breaking down the endocannabinoid anandamide.

With moderate use, these interactions are likely to enhance the body's ability to respond to changes in its various systems and quickly return them to a state of healthy balance.


  • CBD can be extracted from low-THC hemp plants and used as a food supplement.
  • According to the 'entourage effect' theory, CBD may work in synergy with other cannabinoids and plant nutrients when consumed.
  • It can indirectly influence human endocannabinoid receptors by blocking enzymes.
  • It may allow your body to produce higher levels of the beneficial endocannabinoid anandamide.
  • It interacts with several hormone systems.


How do cannabis and alcohol affect driving?

In the UK, between 2013 and 2018, about 6000 car accidents were caused each year by drink-driving. Although there is no direct comparison available for THC, in 2012, the BBC reported on a review of several studies that concluded, "Drivers who use cannabis up to three hours before driving are twice as likely to cause a collision as those not under the influence of drugs or alcohol".

While both appear to significantly impair the user's ability to drive safely, the specific effects of the intoxication of each substance is very different. When alcohol is consumed, the effect is broadly similar from one person to the next, but the effects of cannabis can vary considerably from person to person.

Alcohol is likely to increase risk-taking behaviour, impair the ability to judge distance, slow reflexes and even cause blurred vision. Cannabis affects judgement and coordination. It also impacts concentration and slows reaction times. However, as demonstrated on Channel Five's Fifth Gear, in some cases of moderate use, the difference isn't always noticeable.

In 2010, another study found that people who drive after using cannabis were more aware of the impairments, making them able to adjust their driving style as necessary. It also noted that alcohol was much more likely to impair driving and that "people who smoke marijuana share qualities—being young, male, and risk-taking—that would increase their risk of road traffic accidents even in the absence of marijuana use."            

Will taking CBD affect my ability to drive?

CBD is non-intoxicating and won't impair your ability to drive; however, you must be certain the product you've chosen is THC-free. To verify this, you can check the third-party lab results that retailers should make available on their website.

However, you should always be mindful of your fitness to drive. Whether you've taken any supplement or not, it’s your responsible to check that you're in a fit state to drive before you get behind the wheel.



  • Increases risk-taking behaviour
  • Impairs distance judgement
  • Slows reflexes
  • Blurs vision


  • Impairs coordination
  • Impairs judgement
  • Affects concentration
  • Slows reaction times
  • Drivers may make adjustments to attempt to compensate.


  • THC-free products from trustworthy retailers are non-intoxicating.


Are alcohol and cannabis equally addictive?

According to Public Health England, an estimated 602,391 people were dependent on alcohol in England during the 2018 to 2019 tax year. Drinking alcohol triggers the release of hormones that make us feel pleasure and reduce pain. Continued use can change brain chemistry, making people more susceptible to continue to drink and become addicted.

Recently scientists have been able to show that there is a genetic component to alcoholism, meaning that some people are genetically more likely to become alcoholics than others. However, there is no single factor responsible for someone abusing alcohol. In most cases, it's the combination of several factors, such as mental health conditions, risk-taking behaviour, a long history of drinking, family, environment, age, education, and job.

Once addicted, alcoholics face the struggle of detoxification if they try to stop. Because the brain becomes more used to such high levels of alcohol, when it's no longer there, the withdrawal can produce symptoms that can include sickness, shakes, depression and anxiety.

29.6% of people aged between 16 and 59 have used cannabis at least once, and many people start and stop using it with no symptoms of addiction. However, for some people, cannabis is habit-forming and long periods of frequent use can become 'marijuana use disorder'. This, in severe cases, can develop into addiction.

Dependence on cannabis is defined as regular use that produces symptoms of withdrawal if the user suddesnly stops taking it. Like with alcohol, the brain adapts to high levels of THC and produces negative symptoms if the drug is removed. With THC, withdrawal includes irritability, trouble sleeping and cravings. Some studies suggest that 9% of cannabis users will become addicted, or 17% if they started when they were a teenager.

How many deaths are caused by alcohol and cannabis per year?

In 2019 cannabis-related deaths in the UK reached 31 which was its highest in 25 years. However, 7,565 were attributed to alcohol. The number of people drinking alcohol is considerably higher than those using cannabis, but the difference in these numbers still demonstrates the dangers of alcohol.

Also, 31 cannabis-related deaths don't mean that 31 people died as a direct result of cannabis. The Office for National Statistics (ONS) shows that between 2001 and 2017, a total of only 22 deaths had cannabis mentioned on the death certificates with no other drugs or alcohol present. However, even in these cases, other factors were also mentioned, such as mental and behaviour disorders, circulatory and respiratory disease, injury, poisoning and external causes of death.

How much alcohol do you need to consume for it to be fatal?

A blood alcohol level of over 0.4% is considered to be fatal for most people, although heavy drinkers may be more tolerant. To reach this level of alcohol depends on several factors, including your weight, what you're drinking and how fast you're drinking it.

For an adult weighing 60kg, the lethal amount would be about 300g which is about 1 litre of spirits. However, it would need to be drunk all at once because their liver would go to work detoxifying it if it was consumed at a slower rate. Alternatively, a more significant amount consumed slowly could also produce alcohol poisoning which can result in a coma or death.

How much THC do you need to consume for it to be fatal?

Less is understood about the toxicity of THC because death from THC is much rarer than alcohol poisoning. So far the only recorded cases of THC toxicity causing death may be because it exacerbated preexisting health conditions.

According to research conducted by Benno Hartung et al. in 2014 the amount of THC that gives a 50% chance of death is 30mg per kg of body weight. An 80kg adult would need to consume 2.4g of pure THC to reach this level.

If a person smokes 1 gram of cannabis, they will absorb about 14.6-66.3mg of THC. This means that they would have to smoke 36g or about 1.3 ounces of cannabis (assuming the higher absorption rate of 66.3mg) to reach this level of toxicity. In most standard forms of consumption (smoking, vaping or edibles) it would be difficult to consume this much in one go.

In another study conducted with dogs and monkeys it was found that "single oral doses of Δ9-THC and Δ8-THC between 3000 and 9000/mg/kg were nonlethal." If this was the same for humans it would mean that an 80kg adult could safely consume up to 750g of pure THC or 51.3kg of cannabis before it became toxic.

How much CBD do you need to consume for it to be fatal?

CBD has an excellent safety record, and the World Health Organization reported, “CBD is generally well tolerated with a good safety profile”.

There are currently no studies to indicate if it’s toxic when taken in large amounts, but trials with monkeys in 1981 demonstrated that daily doses of 30-300mg per kg of body weight had little effect apart from slightly increasing the mass of the animal’s liver and kidneys.

There is likely a concentration at which CBD becomes toxic, but current research indicates that it will either be the same as THC or higher.

Cannabis vs alcohol

While cannabis has many negative connotations and is considered by some to be a gateway drug, in comparison it’s considerably safer than alcohol. Using cannabis is less likely to cause death or develop into addiction. Also it has many more positive characteristics that could be utilised in the future should cannabis ever be legalised and correctly regulated.

In the meantime, CBD oil offers a useful and safe way to enjoy some of the benefits provided by cannabis plants.