Introduction
Depression is defined by the Oxford dictionary as “A mental condition characterized by feelings of severe despondency and dejection, typically also with feelings of inadequacy and guilt, often accompanied by lack of energy and disturbance of appetite and sleep”. According to the World Health Organization, 350 million people suffer from depression worldwide, that being 5% of the worlds population, at any given time. Therefore, depression is a common and severe issue that is relevant for many people, and finding a solution to the illness is greatly demanded. Antidepressants have been around since the 1950’s, with varied success since then. Recent research has seen the rise of cannabis being used to treat those suffering from depressive episodes.
Cannabis is a drug that is made from the dried leaves and flowers of the hemp plant cannabis sativa. It is made up of two main chemical components. The first is tetrahydrocannabinol, known more commonly as THC, which gives the plant its psychoactive effects. The second is Cannabidiol, known as CBD. It has grown naturally in the wild for centuries.
The topic of using cannabis as a form of medicine is one that is discussed frequently around the world in today’s society. Due to legal implications due to the prior illegality of the substance, studies into the positive and negative effects of its use on physical and mental health are only now appearing. When researching this topic, I found interesting the supposedly contradicting studies surrounding whether cannabis actually aided or benefitted mental health, more specifically whether it worsened or improved depression and anxiety. With a topic so relevant in todays society, I wondered could looking into the the compounds of different strains of cannabis and also looking at how these react with neurotransmitters in the brain. This lead me to come up with the research question, “To what extent can research into the positive and negative effects of cannabis use help us to develop more effective cannabis based interventions for mental disorders?”
Due to the complexity of the cannabinoid system in the brain, there is conflicting evidence about the effects of THC on the dopamine system, with some studies saying it suppresses it while others suggests that it increases dopamine release.
While cannabis products are more frequently used for pain management, there are a growing number of studies that suggest that cannabis could help patients suffering from mental illnesses. While the majority of this research is about the short term effects of the drug due to the difficulty in studying this mostly illegal drug in most countries, the benefits explained through science can still show the positive benefits that this could have for sufferers of mental illness.
Biology of Depression
Depression is caused by imbalances of chemicals in the brain, more specifically it has been linked to imbalances of neurotransmitters such as serotonin, dopamine and norepinephrine. These neurotransmitters and their receptors are what antidepressant medications aims to alter.
Serotonin is involved in various processes such as sleep, mood, hunger and others. When these are altered due to a decrease in serotonin production, it can cause depressive symptoms such as loss of appetite or low mood to manifest.
The catecholamine hypothesis emerged in the 1960’s as a hypothesis for the cause of depression. It suggested that depression is caused by a lack of catecholamines, particularly the neurotransmitter norepinephrine. Autopsy’s performed on people who had suffered from multiple depressive episodes did support this theory as they had significantly less norepinephrinergic neurons in the brain. However more recent research shows that some people who have had depressive episodes actually have more norepinephrinergic neurons. Also, other studies have shown that a decrease in serotonin production also triggers a drop in norepinephrine, which leads to depression, so serotonin plays a key role in depression.
Lastly, dopamine is said to play a role in the development of depression. Also, dopamine causes us to have a drive towards a goal, and gives us a sense of pleasure during tasks.
Effect of THC
Substances that trigger dependencies have been found to all trigger an increase in dopamine production. When looking specifically at cannabis, the euphoric, relaxed and happy sensation felt while ‘high’ is almost entirely due to the THC components interaction with the cannabinoid receptors that are found almost everywhere in our brain and in other parts of the body and are part of the endocannabinoid system. The effects of cannabinoids such as CBD are controlled and mediated by the cannabinoid receptors, mainly CB1 and CB2 receptors, which are types of cannabinoid receptors. CB1 receptors appear in high quantities in several parts of the brain and mainly mediate psychoactive effects of cannabinoids.
These cannabinoid receptors are bonded by a molecule called anandamide, which regulates mood, as well as other functions. This in turn changes the activity of multiple intracellular enzymes which in short reduces the amount of neurotransmitters released. This can greatly reduce the activity of the brains neural networks. Below are some of the physical symptoms of clinical depression as described by the NHS.
• Moving or speaking more slowly than usual
• Changes in appetite or weight
• Lack of energy
When looking at these symptoms, the effects to neurotransmitters mentioned prior resulting in the lack of brain activity can cause these symptoms above. Therefore, forms of cannabis with the THC component present could possibly cause an increase in severity of symptoms in sufferers of depression, possibly worsening the condition. However, the THC does cause something else to happen in the brain. The main source of dopamine in the brain, the dopaminergic neurons are one of the few places where there are no known CB1 (cannabinoid receptors), but the release of dopamine is usually prohibited by GABAergic neurons which do have CB1 receptors. With the effect of the CB1 receptors mentioned above, this results in the decrease of release signalling from GABA neurons.
As a result, there is no inhibition of the release of dopamine and therefore more is released into the body. In a paper by David J Diehl, he discussed the findings that decreased dopamine activity is linked to depression in humans and is explained in the chapter above in greater detail as being a cause of depression. Therefore, the increase in dopamine production caused by the cannabis and more specifically the THC may in fact be beneficial to sufferers of depression, if the adverse physical reactions can be tolerated.
Effects of CBD
While THC is an influencer in the levels of the neurotransmitter dopamine, the other main component of cannabis, Cannabidiol (CBD) has an effect on the production of serotonin. Cannabidiol is the non-psychoactive component of cannabis. Unlike THC, CBD has little binding effect on the cannabinoid receptors CB1 and CB2. It does however activate multiple non-cannabinoid receptors and ion channels. At high concentrations it directly activates the 5-HT1A (hydroxytryptamine) receptors. This is important because the 5-HT1A receptor is a subtype of serotonin receptor found in the presynaptic and postsynaptic regions of the brain, regions that are known to control mood, cognition and memory. The role of 5-HT1A receptors in depression has been supported in various studies. Many antidepressants, such as SSRI’s, specifically target these receptors to increase signalling. In a paper by Savitz, J (2017), it is discussed how in post-mortems of suicide victims, significantly less 5-HT1A receptors were discovered in these brains. Also, it has been found through genetic studies that dysfunction in the endocannabinoid system, which includes the cannabinoid receptors such as CB1 and CB2, is linked to mood related disorders, including depression. Other studies have found a dysfunction in the CB1 receptor specifically is reported in those with psychiatric disorders.
Long-Term Studies
However, many studies seem to suggest that cannabis has the opposite effect, and that it can in fact increase chances of developing mental disorders such as depression. A 15 year follow-up of a community sample of 1920 participants in a study (Bovasso GB 1980) appeared to show that those that used cannabis were four times more likely to develop depression, as well as an increase in suicidal ideation, suggesting that cannabis has a negative effect long-term. However, in this study, the participants using cannabis were referred to as abusing the drug. This therefore suggests that the cannabis here was not being used in a regulated and medically sensible way and instead in a reckless way. This leaves doubt as to whether this is an accurate representation of what medical cannabis what actually do as a controlled dosage of cannabis may have shown different results on these participants. A similar Australian study (Patton GC 2002) also suggests that long-term cannabis use can cause increase risk of developing mental illnesses. In this study the cannabis use of 1601 14-15 year olds from the Australian state of Victoria was recorded for seven years. This study suggested that there was a positive correlation between the amount of cannabis used and illnesses such as depression and anxiety, with those using cannabis more frequently showing higher rates of these mental illnesses. Those using cannabis at least once a week had approximately a twofold increase in risk for later developing depression. However, the disadvantage of studies similar to this is that they rely heavily on the qualitative data. For a start these types of studies can’t be considered to be representative of the general population. This is because they both include only children from one particular area of the world so it can’t be said to represent all children. Also this research doesn’t establish a cause and effect relationship between cannabis use and depression, it only shows that there is a link between the two. The problem of social desirability might come into play here also, as cannabis is an illegal recreational drug and the participants desire to appear in a positive light may mean that they underestimate or ignore all together any cannabis use that did occur. Another issue when looking at the evidence for using cannabis to treat depression is that the majority of the participants for these studies are children. At a time when the brain is still developing, cannabis could possibly be more harmful to this age group than those that are older. The same effect can be seen when children use prescribed antidepressants such as Prozac. There are a small percentage for whom suicidal thoughts and depressive feelings are actually worsened instead of improved. This indicates that it may not be the cannabis specifically that causes a worsening in depression in children, but just a risk that all children taking this type of medication may have to incur, simply due to the fact that their brains are not yet fully developed. More research would have to be done into adults use of cannabis in order to see if the same results would occur, in which case cannabis may not be a safe antidepressant after all.
What’s limiting about these studies is that they show the possible consequences of long-term use, but the explanation as to why this happens is very limited as of yet. This means that it’s hard to say if there is any biological basis to the theory that it might increase risk of depression.
Maslow’s Hierarchy of Needs
In 1943, psychologist Abraham Maslow published a book titled “The Theory of Human Motivation”. In this book he describes five levels that he claimed humans strive to achieve in order to gain satisfaction in their lives. These levels are shown below.
“1. Biological and Physiological needs – air, food, drink, shelter, warmth, sex, sleep.
2. Safety needs – protection from elements, security, order, law, stability, freedom from fear.
3. Love and belongingness needs – friendship, intimacy, trust and acceptance, receiving and giving affection and love. Affiliating, being part of a group (family, friends, work).
4. Esteem needs – achievement, mastery, independence, status, dominance, prestige, self-respect, respect from others.
5. Self-Actualization needs – realizing personal potential, self-fulfillment, seeking personal growth and peak experiences.”
The theory states everyone starts by aiming to fulfil their needs from the bottom of the pyramid, starting with physiological needs, and when these have been achieved they move on to trying to satisfy the needs of the next tier. Maslow also suggested that failing to move up the pyramid and fulfil their belongingness and love needs, their esteem needs and self-actualisation may result in mental illnesses, including depression, as people are dissatisfied with themselves. Although many people that are already suffering from depressive episodes may suffer symptoms such as lack of motivation and isolation which may make it difficult for them to reach these top tiers, those using cannabis as medication to treat their depression may result in an exaggeration of these symptoms. This is because, as mentioned previously, the THC which causes the psychoactive effects can also cause lack of motivation and symptoms similar to this to be experienced by the user. This may therefore emphasise the inability to meet esteem needs and self-actualisation which as a result may increase the feelings of depression. Therefore, using cannabis as a medication may not be particularly beneficial to those suffering as it may just cause them to be stuck in a cycle of depression.
However, when critically evaluating Maslow’s theory, there is a lack of empirical evidence to support the theory at all. When deducing the theory, Maslow’s methodology is called into question. He analysed biographies of 18 people he deemed himself to be self-actualised individuals. Therefore, the entire existence of self-actualisation cannot be supported and may be in doubt. So perhaps lack of being able to move up the tiers does not result in any negative consequences as although it seems to make sense in theory, there is no evidence that this is in fact the case and it can’t be accepted as a given by any means.
Conclusion
My research question was “To what extent can research into the positive and negative effects of cannabis use help us to develop more effective cannabis based interventions for mental disorders?”. Through the course of this essay I have achieved a deeper understanding of the possible positive and negative effects caused by cannabis, but also that due to the lack of specific research on the topic, that it is very difficult to say exactly how effective cannabis would be as a treatment for depression, as the studies examined have too many flaws to be able to directly associate them with cannabis treatment.
Until more research is done into the long term consequences of cannabis, its difficult to say whether this would actually be an effective treatment method for mood disorders. Overall, the research seems to show that, when looking at the issue from a more biological perspective, in theory cannabis should be an effective treatment for multiple mental illnesses but specifically depression. However, the qualitative studies seem to suggest that this in fact has the opposite. This is especially suggested by the more long-term studies where it seems particularly worrying the number of people who have reported a long-term adverse effect. However, more research needs to be done on the long-term effects of cannabis on those already suffering from depressive episodes as a conclusion cannot thus far be drawn on how it would impact these people. Therefore, looking at the evidence presented, it is likely that cannabis may relieve the symptoms of depression in the short-run while the CBD and THC is still in the system and therefore, one is still benefitting from its effects biologically. But it’s effectiveness as a long-term treatment for depression is questionable and would be unadvisable until further research is carried out in this area.
When looking back at the research, it seems that the CBD component is on the whole better at treating depression than the THC. This is because, although the THC does cause more dopamine to be released, theoretically relieving the symptoms of depression, the THC, which causes the psychoactive effects, results in multiple undesirable side effects discussed previously that are too closely linked to the symptoms of depression, and so could possibly create more of a problem for patients instead of resolving it. It is currently possible to isolate the CBD component of the cannabis plant to create an oil. This is legal in the UK and is currently prescribed to patients with seizures. Based on the research, it seems that looking into this CBD oil for use as an antidepressant would be beneficial and considering declassification of cannabis as a class B drug would allow the science community to study the clinical benefits of this plant in greater detail, as it is ever increasingly apparent that it has the potential to have major benefits for a wide range of ailments, not only mental illnesses.