Cannabis: the facts – Healthy body
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Cannabis (also known as marijuana, weed, pot, dope or grass) is the most widely used illegal drug in the UK.
The effects of cannabis vary from person to person:
- you may feel chilled out, relaxed and happy
- some people get the giggles or become more talkative
- hunger pangs (“the munchies”) are common
- colours may look more intense and music may sound better
- time may feel like it’s slowing down
Cannabis can have other effects too:
- if you’re not used to it, you may feel faint or sick
- it can make you sleepy and lethargic
- it can affect your memory
- it makes some people feel confused, anxious or paranoid, and some experience panic attacks and hallucinations – this is more common with stronger forms of cannabis like skunk or sinsemilla
- it interferes with your ability to drive safely
If you use cannabis regularly, it can make you demotivated and uninterested in other things going on in your life, such as education or work.
Long-term use can affect your ability to learn and concentrate.
Can you get addicted to cannabis?
Research shows that 10% of regular cannabis users become dependent on it. Your risk of getting addicted is higher if you start using it in your teens or use it every day.
As with other addictive drugs, such as cocaine and heroin, you can develop a tolerance to cannabis. This means you need more to get the same effect.
If you stop using it, you may get withdrawal symptoms, such as cravings, difficulty sleeping, mood swings, irritability and restlessness.
If you smoke cannabis with tobacco, you’re likely to get addicted to nicotine and risk getting tobacco-related diseases such as cancer and coronary heart disease.
If you cut down or give up, you will experience withdrawal from nicotine as well as cannabis.
Cannabis and mental health
Regular cannabis use increases your risk of developing a psychotic illness, such as schizophrenia. 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).
Your risk of developing a psychotic illness is higher if:
- you start using cannabis at a young age
- you smoke stronger types, such as skunk
- you smoke it regularly
- you use it for a long time
- you smoke cannabis and also have other risk factors for schizophrenia, such as a family history of the illness
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
Cannabis can be harmful to your lungs
People who smoke cannabis regularly are more likely to have bronchitis (where the lining of your lungs gets irritated and inflamed).
Like tobacco smoke, cannabis smoke contains cancer-causing chemicals, but it’s not clear whether this raises your risk of cancer.
If you mix cannabis with tobacco to smoke it, you risk getting tobacco-related lung diseases, such as lung cancer and chronic obstructive pulmonary disease (COPD).
You’re more likely to be injured in a road traffic accident
If you drive while under the influence of cannabis, you’re more likely to be involved in an accident. This is one reason why drug driving, like drink driving, is illegal.
Cannabis may affect your fertility
Research in animals suggests that cannabis can interfere with sperm production in males and ovulation in females.
If you’re pregnant, cannabis may harm your unborn baby
Research suggests that using cannabis regularly during pregnancy could affect your baby’s brain development.
Regularly smoking cannabis with tobacco increases the risk of your baby being born small or premature.
Cannabis increases your risk of cardiovascular disease and stroke
If you smoke it regularly for a long time, cannabis raises your chances of developing these conditions.
Research suggests it’s the cannabis smoke that increases the risk, not the active ingredients in the plant itself.
Does my age affect my risks?
Your risk of harm from cannabis, including the risk of schizophrenia, is higher if you start using it regularly in your teens.
One reason for this is that, during the teenage years, your brain is still growing and forming its connections, and cannabis interferes with this process.
Does cannabis have medicinal benefits?
Cannabis contains active ingredients called cannabinoids. Two of these – tetrahydrocannabinol (THC) and cannabidiol (CBD) – are the active ingredients of a prescription drug called Sativex. This is used to relieve the pain of muscle spasms in multiple sclerosis.
Another cannabinoid drug, called Nabilone, is sometimes used to relieve sickness in people having chemotherapy for cancer.
Trials are under way to test cannabis-based drugs for other conditions including cancer pain, the eye disease glaucoma, appetite loss in people with HIV or AIDS, and epilepsy in children.
We will not know whether these treatments are effective until the trials have finished.
Trying to give up?
If you need support with giving up cannabis:
- see your GP
- visit Frank’s Find support page
- call Frank’s free drugs helpline on 0300 123 6600
- see Drugs: where to get help
You’ll find more information about cannabis on the Frank website.
Page last reviewed: 31 October 2017
Next review due: 31 October 2020
How cannabis (marijuana, weed, dope, pot) affects you, the risks and where to find help if you're trying to quit.
What Are the Effects of Mixing Nicotine and Cannabis?
Tobacco and cannabis have a strange relationship, one that has lasted for centuries but has been continually turbulent. Why do so many people use the two together? As usual with cannabinoid science, the truth is stranger than anything that could be dreamed up.
Tobacco and cannabis have been consumed together for centuries by people all over the world. In fact, it is thought that up to 70% of people that use cannabis also use tobacco. Even in North America, where cannabis is traditionally smoked pure, many users also use tobacco.
In fact, it is common in North America to smoke cigarettes immediately after smoking cannabis. This is likely to produce similar synergistic effects to actually mixing the two together (many do so for the perceived experience of getting “more high” as a result).
Differences in effect are widely reported
Many users report subjective differences between the effects of cannabis alone and cannabis when mixed with tobacco.
The most common reported effect of smoking tobacco alongside cannabis is an intensification of the high, although some report that tobacco use actually has the opposite effect and reduces the high. Another commonly reported effect is to calm the user down from the sometimes anxiety-inducing effects of cannabis.
The biological mechanisms behind this strange relationship are wildly complex. They are linked to various other processes now known to be related, but long believed to be essentially separate. The more we learn about these interlinked systems of reward, craving, addiction and satiety, the more we begin to understand that every aspect of our brains and bodies is inseparably intertwined.
Cannabis, tobacco and the hippocampus
A widely-reported recent study correlated long-term heavy cannabis use with reduced volume and density of the hippocampus, an area of the brain that is associated with memory, inhibition and addiction.
This was also demonstrated in this study from 2011, although the effect here was found to depend on various factors including ratio of THC to CBD. More specifically, higher THC and lower CBD was associated with a volume reduction in the right hippocampus. This indicates neurotoxic effects of THC and neuroprotective effects of CBD.
At least one other study has found no long-term change, and one study highlighted the possibility that genetic differences may alter the hippocampal response to cannabis use. This reduction in size was found both in cannabis-only users and in cannabis/tobacco users. It was not found in nicotine-only users, though.
In cannabis-only users, the small hippocampus was found to correlate with poor memory. This is unsurprising, as good hippocampal health and size usually correlates positively with good memory in children, adolescents and young adults. So within the group, the smaller the hippocampus, the poorer the memory.
However, the researchers also found something very surprising: in the cannabis/tobacco-using group the reverse was true, and smaller hippocampal volume correlated with improved memory! Subjects that smoked higher numbers of cigarettes exhibited greater decreases in hippocampal volume, and relatively higher memory scores (although memory was still generally poorer than in all other groups).
While this study was limited in scope and design, establishing correlation but not causation, it still demonstrates an unusual effect, and one that has yet not been fully explained. It is important to note that as a cross-sectional study looking at a brief window of time, it is inferior to a longitudinal study. One which would follow subjects for extended time periods to better track changes and establish causation.
Effects of Cannabis on the Male and Female Reproductive System, and Fertility
How all the main regulatory and signalling systems are linked
It now appears that tobacco, cannabis and other psychoactive substances such as opioids are all linked together in a complex network of stimulus and reward, with the hippocampus essentially functioning as the HQ for operations.
Throughout the body, and particularly in the brain, we have cannabinoid receptors (which are part of the endocannabinoid system) as well as opioid and nicotinic receptors. Within the brain, densities of these receptors are extremely high in the hippocampus and are also very high in the amygdala (both areas are heavily associated with stimulus, reward, addiction and so on).
The agonists (activators) of these three types of receptors (of which the best known are THC for the cannabinoid receptors, nicotine for the nicotinic receptors and morphine for the opioid receptors) are hugely important in terms of the psychoactive and physiological effects they can exert. In fact, even substances that inactivate the receptors (like CBD for the cannabinoid receptors and naxolone for the opioid receptors) are of great interest due to their opposite effects.
How deeply are these systems interlinked?
While we’ve known about these systems for years, we are only beginning to understand the extent and depth of the connections that they have with each other. It is difficult to really see them as separate systems at all, given the innumerable, criss-crossing links that flow back and forth between them.
Here is a brief look at how these systems can affect each other. We know that nicotine itself acts on the opioid (and possibly cannabinoid) receptors, as well as the nicotinic receptors themselves. We also now know that subchronic exposure to nicotine increase the numbers of CB1 receptor in the hippocampus and decrease in striatal cannabinoid CB1 receptors.
We now also know that substances that block the CB₁-receptors can cause people and animals to stop craving both nicotine and morphine. Thus, agonists of the CB₁-receptors may cause increased cravings for nicotine, which may explain the common desire to smoke cigarettes immediately after cannabis, or the heightened subjective level of satisfaction derived from smoking the two together.
In fact, it seems that to get any “rewarding” effect at all from using sugar, nicotine, alcohol or cocaine, we need to activate the cannabinoid receptors; no activation, no release of dopamine and no subject experience of pleasure!
There also appears to be a genetic element to all this — variations in the CNR1 gene (which encodes for the expression of CB₁-receptors) are associated with variations in susceptibility to nicotine dependence. This association is found in white females but not white males (whites were the only race tested in the study).
So what does all this mean?
Well, we’re still a long way from developing a precise understanding of all the different processes that occur in the brain in response to the introduction of psychoactive substances, alone or in combination.
But we are now beginning to come to terms with this vast complexity, and to realise that investigation of any substance use or abuse or any psychiatric illness cannot be done in a vacuum. For example, we can no longer point the finger at cannabis and blame incidences of psychosis solely on its use, now that we are aware of exactly how much influence other factors such as nicotine use may play.
We can now view this vast and interconnected system for what it is and we can make nuanced judgements on individual cases, based on a much wider and more cohesive set of factors, influences and interrelationships.
Acute and Long-Term Cognitive Side-Effects of Cannabis
So how do we put this knowledge into practice?
The interactions between nicotine and THC are complex and heavily dose dependent. It is no doubt dependent on a host of other variables that science is either unaware of or is just beginning to grasp.
Tobacco use has often been overlooked when investigating the cognitive and psychiatric effects of cannabis, despite the established knowledge that nicotine is a psychoactive substance in its own right. This oversight seems even more egregious when considering the extremely high incidence of cigarette smoking among sufferers of certain psychiatric conditions, including schizophrenia.
Indeed, recent research is finally beginning to tackle this subject head on, and has somewhat unsurprisingly found that nicotine is strongly associated with development of psychosis! The author of this recent study, James McCabe of King’s College London, is on record as stating “it might even be possible that the real villain is tobacco, not cannabis”.
Nicotine is generally negative for health and should be avoided. However, studying the differences between users of nicotine and cannabis alone compared to users of both has given us some important insights into the interconnected nature of the brain’s signalling and reward systems.
From this and other relevant research, we now know that the endocannabinoid system is heavily involved in the regulation of stimulus and reward and has a huge part to play in addiction to substances such as nicotine and morphine.
Some say cigarettes boost your high, others say nicotine ruins your high. Here is what the limited research says on mixing cannabis and nicotine.