Common side effects associated with use of marijuana and cannabinoids

Here are some of the side effects discussed (with references) in this post.  Note that they’re associated with cannabinoid use, which means that more people who use cannabinoids tend to experience them.  It does not mean that cannabis use clearly causes these effects.

• Common effects such as drowsiness, dizziness, dry mouth, and poor attention(1)
• Addiction
• Motor vehicle accidents
• Effects on maternal and child health
• Cognition and other neurological effects
• Psychiatric conditions (depression, anxiety, amotivational state)
• Sleep
• Cardiovascular effects
• Respiratory effects
• Cancers

Most adverse effects tend to be mild to moderate, and they don’t cause permanent damage.

Yes, cannabis can be addictive

In a previous post, I discuss a theory of how addictive behaviours develop; in that the experiences required for survival create a sense of pleasure by stimulating the brain’s “reward centre”.  However, it is possible that other things not required for survival (such as drugs) can also cause pleasure in that same reward centre and therefore keep us going back for more.

At least one study shows that 9-10% of people who use cannabis will become addicted. That number increases to 16–17 % for people who start using cannabis as teens, and up to 25–50% for daily users. The risk for addiction seems to reduce with age, so that someone who doesn’t start using cannabis until age 25 rarely becomes addicted.  It has also been found that earlier use of cannabinoids increases vulnerability of use of other drugs (adding support for the “gateway hypothesis”.(1)

Also, heavy users tend to have lower income, greater need for socioeconomic assistance, unemployment, and lower life satisfaction. (1)

Again, these are correlations, and not proof of causation, but I think they are important to note.

Public safety and motor vehicle accidents

Just as with alcohol, the higher the level of impairment with cannabis, the higher the risk of motor vehicle accidents.  In fact, people under the influence of cannabis can be between 2 to 7 times more likely to be involved in both fatal and non fatal motor vehicle collisions.(1)

Effects on maternal and child health

Cannabis use during pregnancy is associated with poor physical outcomes, including birth defects, low birth weight, and an increased risk of childhood cancer, as well as poor neurodevelopmental outcomes, including aggressive behavior and attention problems in girls. For example, children who were exposed to marijuana prenatally are more likely to demonstrate decreased problem-solving skills, as well as poor memory and attention. Similarly, babies exposed to marijuana prenatally show traits indicative of neurological development problems.(1)

Neurological and mental health effects of marijuana and cannabinoids

Cannabis is well known to reduce many aspects of memory, impair IQ and attention, and to reduce inhibitions.(1, 2)

The risk of long-term neurological effects increases the more someone uses cannabinoids and the younger they are when they start.  However, many of the impacts from short-term cannabis use are reduced after discontinuing them.(1)

Interestingly, recent neuroimaging studies have shown some structural abnormalities in areas of the brain high in CB1 receptors in people who use cannabis regularly.  In fact, there was more significant abnormalities in people who use more cannabis.(1)

There is also evidence of an association between cannabis use and mental illness, including depression, anxiety, psychosis, bipolar disorder, schizophrenia, and an amotivational state.  These links are complicated and (again) they are just associations, not causation.  In fact, it is thought that cannabis use doesn’t necessarily cause, but rather exacerbates pre-existing mental health issues like bipolar disorder and schizophrenia.

The associations between cannabis and anxiety are complicated because it is thought that low levels of THC reduces anxiety, while higher levels can increase it.  This is also affected by the level of CBD which can interact with these THC effects.(1)

Sleep is a common side effect of people who take cannabinoids.  This can be beneficial for some.  Studies have shown, however, that while cannabinoids can increase duration of sleep, the quality of that sleep is lower.(1)

Non-neurological side effects of marijuana and cannabinoids

Long-term cardiovascular and respiratory consequences of cannabis use are fairly well evidenced. (1)

It is recommended that people with cardiovascular issues avoid marijuana because of its effects on the heart, such as angina, heart attacks and death.(1)

While cannabis is not tobacco nor does it contain nicotine, it does contain several harmful toxins when burned and inhaled.  Some known respiratory adverse effects of smoking marijuana include inflammation, bronchitis and emphysema.(1)  Smoking is therefore not a recommended way to consume cannabis.(2)

Cannabis’ contribution to lung cancer risk is unclear.  Some studies have shown no increased risk, others showed increased risk.  Some analyses of the smoke showed that it was similar to tobacco smoke, others show it has higher levels of cyanide and aromatic amines.(1)

In terms of other (non-smoking related) cancers, at least one study has shown an increased risk for prostate and cervical cancers, as well as glioma.(1)

Because there are CB2 receptors on immune cells, effects of cannabinoids have been studied there as well.  Again, there have been controversial results with some studies showing immune suppression, and others showing anti-inflammatory and neuroprotective effects of CBD.  Interestingly some studies have found that the body’s naturally occurring endocannabinoids can have an immune-enhancing response, while consumed cannabinoids can suppress the immune system.(1)

Things to consider before using cannabinoids

A significant amount of research still needs to be done regarding cannabis and pain to further understand the risks and benefits.  This would include more research in the different doses of the compounds, as well as the different ways to consume it.

However, when recommending medical cannabis, physicians and patients would benefit from discussions of the risks, benefits, and uncertainties associated with cannabis use. Furthermore, medical cannabis should be avoided in vulnerable populations, including individuals under the age of 25 years, individuals with current or past substance use disorders, individuals with a personal or family history of mental illness, those that have compromised cardiovascular, respiratory, or immune systems, and those who are pregnant.(1)

When it comes to pain we must remember the side effects and medical issues regarding opiods and overdoses. “However, a careful consideration of the risks and benefits of cannabis for pain along with further research into its efficacy is necessary to ensure that one controlled substance problem is not simply replaced with another.”(3)

References:

(1) Safety and Toxicology of Cannabinoids

(2) Effectiveness, Adverse Effects, and Safety of Medical Marijuana

(3) Medical Marijuana and Chronic Pain: a Review of Basic Science and Clinical Evidence