Medicinal Although there are a number of medical conditions for which the therapeutic properties of cannabis and its by-products are now unquestionable, there continue to be disorders or pathologies for which its benefits are not quite as clear. Similarly, even though for some psychiatric pathologies the risks associated with the use of cannabis are fairly well defined, for others, the risks are relatively unknown.
The use of cannabis and mental health
It is likely that among all these potential uses for which the scientific information is less clear with regard to the possible mental health consequences for cannabis users, it is its relationship with depression that is the most uncharted territory.
This is because, despite one of the functions of endocannabinoids being mood regulation, it still isn’t entirely clear whether the use of cannabis by people suffering from depression could be beneficial, harmful or, have no effect at all.There is also very little data available on the relationship between consuming cannabis and developing symptoms of depression, even though there are numerous investigations that attempt to establish a causal relationship between consuming cannabis and the appearance of other mental disorders such as for example schizophrenia (a relationship that no study has yet been able to demonstrate conclusively as causal). Conventional wisdom would have it that you can’t generalise, that some people will benefit whereas others won’t, to a greater or lesser extent, that someone will have a friend who cured his or her major depression by smoking cannabis, someone else will have a friend who was able to give up his or her medication thanks to smoking joints, and others still will have a friend whose depression was caused by smoking joints, resulting in a whole array of cases of every possible description. Conventional wisdom wouldn’t be far wrong. These case studies are probably a more faithful reflection of the reality in the case of the relationship between cannabis and depression than in other cases, where these relationships can appear more tenuous. At least this is what a recent study published in the prestigious scientific journal Addiction Biology seems to infer.
Depression is without a doubt the major health issue of the developed world. According to the World Health Organization, it affects 121 million people today in every part of the world. It is the leading cause of disability and affects people of every age, gender and circumstances. The main symptoms are a depressed state of mind, loss of interest or pleasure in daily activities, feelings of guilt or low self-worth, poor concentration, disturbed sleep or disturbed appetite and low levels of energy. Depression can end in suicide, a tragic end responsible for 850,000 deaths every year.
The role of genetic predisposition
Although the study I describe here was not designed to research the possible uses of cannabis for treating depression, but rather to research if there is any relationship between cannabis consumption and developing symptoms of depression, the results are so interesting that they could serve to better understand, from a therapeutic point-of-view, the potential benefits or potential harm that could result from recommending cannabis to someone suffering from depression. It also helps to better understand why it seems that some people, when it comes to their emotional well-being, benefit from cannabis while others suffer such ill effects.
The study was longitudinal, i.e. it followed a group of 310 adolescents over a period of four years. Every year, the adolescents completed tests where symptoms of depression were evaluated and genetic tests were carried out to determine their genetic vulnerability to depression. It seems necessary to open a parenthesis here. Is it possible to determine genetic vulnerability to depression?
The importance of the vulnerability of the individual
As with all mental health issues, the causes of depression are varied. Although genetic conditioning and environmental conditioning can vary depending on the type of disorder, in terms of mental illness, there are no disorders that are purely genetic or purely environmental. It is rather a case of a particular genetic difference that can predispose someone–or make a particular individual more vulnerable–to suffering from a mental disorder if that person is exposed to an environment that facilitates the onset of such a disorder. There can be a genetic predisposition that–unless the person is exposed to a conducive environment–doesn’t develop into an illness, in the same way as being continuously submitted to extreme conducive environments can end up triggering a disorder in people who are less genetically predisposed to it. For example, people with a genetic vulnerability to schizophrenia could in fact never develop it because they have never been exposed to the stressful environments that can trigger schizophrenia, in the same way as people without this vulnerability could develop mental illness because they have suffered traumatic events such as physical torture.
However, there is a biological marker of vulnerability to depression, which is a gene that encodes the presence of serotonin transporters in the brain.The serotonin transporter is a protein responsible for regulating the quantity of serotonin in our nervous system. It is like a recycling pump that by carrying serotonin from outside to inside a neuron and back again ensures an equilibrium in the brain that makes it feel emotionally stable. There is a type of gene that encodes this protein, i.e. activation of this gene gives the order to produce serotonin reuptake proteins. Each gene has two alleles. If this gene in particular has what is known as the long allele (which only means it is composed of a larger number of bases than the short one), it will encode more serotonin transporters. If it has the short allele (i.e. fewer bases), it encodes fewer serotonin transporters. As a result, it appears that people with the short allele are more prone to depression than those with the long allele.
Research on the influence of genes
The investigators of this study followed the two children of each of the 428 families studied by giving them tests to evaluate depression, as well as determining the gene expression of 310 of them.They also studied their consumption of marihuana.What they found was that the adolescents that had the short version of the gene that encodes the serotonin transporter had more symptoms of depression in the long term than those with the “long” version of the gene.The direction of causality was also clearly established: it wasn’t that the adolescents developed symptoms of depression because they had the short allele of the gene and as a result, self-medicated with marihuana.The direction of causality was rather the opposite: the adolescents with the short allele of the gene who smoked marihuana had more incidence of symptoms of depression in the long term.This means that smoking marihuana transpired to be an environmental cause that triggered depression in people who were already genetically predisposed. This was even the case despite the fact that the adolescents with the short allele of the gene felt euphoria and the other pleasurable effects associated with marihuana when they started to smoke it.Other environmental variables associated with depression in adolescents were studied, such as the use of tobacco and alcohol, the level of education, and socioeconomic and personality factors.
In summary, this interesting investigation is the first to show a solid link between the consumption of cannabis, and depression and its symptoms.Even though it doesn’t answer the question of whether marihuana could be a useful treatment in depression, it does seem to answer the question of whether its use constitutes a trigger for problems with depression. It transpires that this is the case in people with a genetic predisposition, for whom smoking marihuana is not advisable. The rest of the population appears to be off the hook. There are some questions that have yet to be answered though such as: can cannabis be useful to people who don’t have this genetic vulnerability but do have depression?Could it be that this variability in effects that we discussed at the beginning of this article with respect to the difference in effects that cannabis has in people with depression responds precisely to this genetic difference that exists between individuals?These are questions that need to be answered in future studies. In any case, I don’t know whether someone can go to their GP and request a genetic analysis to determine their vulnerability to depression so it is perhaps better for people to observe themselves closely and decide for themselves whether consuming marihuana has a good effect, an ill effect, or no effect at all…and act accordingly.
Author: José Carlos Bouso