Tetrahydrocannabinol (THC) is the most abundant cannabinoid found in most cannabis cultivars. Its therapeutic value has been overshadowed by its intoxicating effects—when you smoke pot, THC is what gets you high. Is THC a medicine, or is it recreation?  What are the side effects of THC?

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Side Effects of THC

THC stimulates CB1 and CB2 receptors. Since these receptors collectively pervade most organ systems, THC has a range of side effects, many of which are outlined in the Textbook of Family Medicine 9th Edition.  We’re only going to focus on short-term side effects of consumption, since there are so many factors that go into long term effects outside of THC. 

Desired side effects 

Those looking to consume THC are typically searching for the more positive effects of cannabis. In 2008, Canadian researchers studied 41 adults to understand why they use cannabis. The self-reported desired effects were:

  • Euphoria
  • Psychotropic effects such as:
  • Relaxation
  • Carefreeness
  • Appreciation for the arts
  • Altered State of Consciousness
  • Increased libido
  • Heightened sensations

Neutral side effects

There are a number of side effects that are much more subjective and are therefore labeled as neutral for the sake of categorization:

  • Sudden hunger
  • Thirst

Adverse side effects

According to the Textbook of Family Medicine 9th Edition, adverse side effects can include:

  • Anxiety
  • Paranoia
  • Delusions
  • Hallucinations
  • Trouble Concentrating 
  • Dry mouth
  • Impaired perception and motor skills

How THC Works 

The endocannabinoid system (ECS) is a neuromodulatory system that plays an important role in regulating many bodily functions.  Sleep, pain perception, metabolism, mood, and immunity are some examples of physiological processes the ECS facilitates, either solely at some receptors or working in combination with other hormone or neurotransmitter systems. The ECS is comprised of three agents:

  • Endocannabinoids. N-arachidonoylethanolamine (anandamide/AEA) and 2-arachidonoyl glycerol (2-AG) are the most well researched endocannabinoids, neurotransmitters that deliver messages to the brain by binding to cannabinoid receptors. 
  • Cannabinoid receptors. CB1 and CB2, members of the G protein-coupled receptor family, are located throughout the body. These receptors carry messages from neurotransmitters like endocannabinoids to the brain, and those messages initiate physiological processes.   
  • Enzymes. Degradative enzymes such as fatty acid amide hydrolase (FAAH) aid in metabolizing endocannabinoids. These enzymes break endocannabinoids down so that they become inactive, an important function in the maintenance of homeostasis; too many or too little active cannabinoids can disrupt normal physiological functioning.  

THC, a phytocannabinoid, has demonstrated a binding affinity for CB1 and CB2. This means that THC transmits messages to the brain through its interactions with CB1 and CB2. THC has a particular attraction for CB1 receptors which are densely located in the central nervous system. While THC also activates CB2 receptors which are located throughout the body and associated with the immune system, it is most well-known for the psychoactive effects it induces through its activation of CB1.   

Can You Overdose on THC? 

On its own, THC is not toxic enough to result in a fatal overdose. However, it is still possible to consume more of the compound than the ECS can handle.

  • Signs of a THC overdose:
  • Anxiety
  • Paranoia
  • Nausea
  • Extreme Fatigue
  • Disorientation
  • Rapid Heart Rate

Complications related to these temporary symptoms can result in fatal events. For example, consumers with a history of cardiovascular illness may experience serious complications following cannabis use, 25% of which result in death according to a 2014 Journal of the American Heart Association study However, the study doesn’t mention other cardiac risk factors such as cigarette smoking. The France-based research team cautioned medical practitioners to:

“be aware that cannabis may be a potential triggering factor for cardiovascular complications in young people."

THC-induced psychosis may also cause erratic and potentially fatal behavior. One well known incident in Colorado involved the tragic death of a 19-year-old man who jumped off of a 4th story balcony after consuming an entire cannabis infused cookie containing approximately 65 mg of THC.

While THC will not directly shut down breathing and heart rate the way opioids or alcohol can, it can cause acute symptoms of psychosis and may trigger cardiovascular effects.

THC Plays an Important Role in Producing Cannabis’ Therapeutic Effects  

A 2019 University of New Mexico study by Stith et al. shed light on THC that may finally redeem the controversial cannabinoid.

The study, published in Scientific Reports, made the remarkable conclusion that THC may be even more important for therapeutic effects than CBD, a non-psychoactive cannabinoid that has been the central subject of most cannabis research in the last several years. Interestingly, dried flower was also most commonly associated with better symptom relief than other types of products.

However, the study notes that it could be the combination of THC and CBD that makes the consumer aware of CBD’s effects. More studies are needed to determine any synergistic effects between the two, instead of studying them in isolation.

Stith et al. gathered data from the ReleafApp, a database of self-reported patient information about the effect of various cannabis products and their consumption methods. The data included records documenting 19,910 cannabis sessions by 3,341 people between June 2016 and March 2018.

The researchers found that high levels of THC were independently associated with both greater symptom relief and a greater occurrence of side effects. Increased levels of CBD, on the other hand, were not associated with symptom relief or side effects.  Although the observational nature of this study limits its authority, its findings encourage further research, and perhaps a bit more optimism about the psychoactive medicine. 

THC’s Effects are Dose Dependent 

Stith et al.’s research partially supports the findings of a 2017 study by Emma Childs, Joseph Lutz, and Harriet de Wit. The University of Chicago-based research team determined that THC’s effects on stress were dose dependent—higher doses were associated with worse outcomes. 7.5 mg THC was found to reduce stress levels while 12.5 mg THC worsened overall mood.

If you are interested in consuming cannabis, consult with your doctor. Microdosing cannabis may be a way for you to find the right dose of THC for your body. In a country where alcohol and tobacco are legal despite knowledge of their toxic and carcinogenic effects, it does not seem fair to label THC as an unsafe substance without further scientific investigation.

However, it is also important to acknowledge the risks of consuming an elusive compound that is both medicine and recreation.  

This information is presented for educational purposes only, and is not intended to diagnose, treat, cure or prevent any medical condition.  Please always consult your own doctor.