Help is here. You are not alone
Table of content
Table of content
All About Recovery
Facebook Group • 2213 members
There's always clouds before the rainbows. Join many others who are going through the same thing as you and see proof that it can get better.

Side Effects of Weed: The Dangers of Marijuana Use

Side Effects of Weed: The Dangers of Marijuana Use
Written by Seth Fletcher on October 12, 2023
Medical editor Dr. Chintan Shah
Last update: March 3, 2024

Weed is one of the world’s most controversial substances. It remains the most widely cultivated, abused, and trafficked illicit drug. In recent years, many countries, including Canada, have legalized the use of marijuana for medicinal or recreational purposes. This move has caused a surge in the number of people who use marijuana. Also known as cannabis or marijuana, weed is a psychoactive herb that affects the mind and body. Currently, perceptions about marijuana use are changing. Many, especially young people, no longer see marijuana for the dangerous substance that it is. 

Marijuana abuse can cause significant long and short-term physical and psychological side effects. People who abuse marijuana may also develop cannabis use disorder. Research shows that 30% of weed users will develop cannabis use disorder. It’s vital to understand the potential dangers of weed and how it affects the body before using it. The Canadian Centre for Addictions guide explains all you need to know about the side effects of weed so you can make informed choices regarding its use.

Key Takeaways

  • Weed is a psychoactive plant that affects the mind and body in multiple ways
  • Tetrahydrocannabinol (THC) is the chemical responsible for weed’s mind-altering properties 
  • Abusing weed can lead to severe short and long-term physical and psychological side effects
  • Weed also has medicinal properties that make it helpful in managing several ailments
  • It’s essential to speak with a professional before attempting to treat any condition with weed

Risk Factors for Marijuana Use

Man drinking some medicines feeling bad or having hangover after the alcohol party, sitting on the couch at home

It’s challenging to pinpoint why people use or abuse marijuana. However, some agreed-upon concepts may explain why people use the drug. Marijuana is smoked, vaped, cooked into food, or brewed with tea (edibles). Cannabis products may also be used topically or as part of an oil. The risk factors for cannabis use include:


Individuals with a family history of substance use or addiction are more likely to use marijuana at some point. Research shows a connection between members of the same gene pool and addiction rates. 

Environmental and Social Factors

People who grow up in environments with easy access to marijuana and other substances have a higher chance of abusing and becoming addicted to weed. Peer pressure and the need to feel accepted can also make young people in these settings try weed. The earlier people are exposed to these conditions, the greater their chances of abusing weed. 

Pre-Existing Mental Health Conditions

People with conditions like anxiety or depression may self-medicate with marijuana. The absence of quality medical care may also prompt some people to turn to substances.

History of Trauma 

Individuals who have had to deal with traumatic experiences such as violence or neglect may use marijuana as a coping mechanism for unpleasant memories or feelings.


Individuals going through high levels of physical or emotional stress may use marijuana as a means of stress relief.

If you or a loved one is abusing cannabis or dealing with cannabis use disorder, there may be a need for professional intervention. The Canadian Centre for Addiction offers sophisticated substance abuse and addiction treatment in an environment that inspires lasting change. At CCFA, we help people understand their addictions and the healthier coping strategies available by engaging them in one-on-one counselling with certified counsellors, psychiatrists, and mental health professionals. Contact us at 1-855-499-9446 to learn more about our services.

Short-Term Side Effects of Weed

Weed contains Tetrahydrocannabinol (THC), a psychoactive chemical that triggers several physical and psychological symptoms. Some side effects of cannabis show up within a short period and include:

Poor Memory and Learning Ability

THC alters the hippocampus, the area of the brain responsible for processing information and forming memories. This action impairs a user’s ability to learn or retain information for short periods. 

Difficulty Thinking and Solving Problems

Weed’s effects on the brain can also impair executive functions, making it challenging for users to make decisions or solve problems.

Poor Muscle Coordination

THC also interacts with receptors in the cerebellum and basal ganglia, areas of the brain that regulate posture, balance, coordination, and reaction times. Higher doses of THC impact muscle coordination and fine motor skills. 

Increased Appetite 

THC increases appetite by binding to receptors in the tongue and making food taste better. It enhances how your brain responds to sweet food and increases your desire for fatty foods. Cannabis can also make the brain think you’re hungry, even if you’ve recently eaten.

Altered Perception of Time and Space

The euphoria that comes with cannabis use may cause distorted perceptions of time and space. Users may feel more sensitive to stimuli and less inhibited. These feelings, combined with impaired coordination, can make driving or operating machinery dangerous. 

Other short-term cannabis side effects include:

  • Hallucinations
  • Mood swings
  • Increased heart rate
  • Slowed breathing 
  • Panic attacks
  • Bloodshot eyes
  • Paranoia 
  • Psychosis 

Long-Term Side Effects of Weed

Weed use can cause long-term side effects that remain even after the user quits the drug. The long-term side effects of marijuana depend on the following factors:

  • Mode of use
  • Frequency of use
  • Age of the user 
  • Quantity of weed use
  • Strain of marijuana used or THC content

Weed Addiction

About 30% of people who use weed become dependent or addicted. Weed’s addiction potential comes from the action of THC on cannabinoid receptors in the brain. THC molecules cross the blood-brain barrier and activate the brain rewards system. They trigger dopamine release, leading to the associated high. This dopamine surge prompts the repeat of reward-seeking behaviour, leading to potential dependence and addiction. Individuals who have become dependent or addicted to marijuana will experience weed withdrawal symptoms if they try to quit or reduce their use. 

Damage to the Respiratory System

Respiratory system damage is one of the most common long-term negative effects of marijuana one can experience, especially from smoking the herb. The cannabis plant contains toxins such as ammonia and hydrogen cyanide, which irritate the lungs and bronchial passages. Regular weed smokers cough and wheeze more and have a higher risk of developing bronchitis and lung infections. Smoking weed can also worsen pre-existing respiratory conditions like asthma and cystic fibrosis. 

Damage to the Cardiovascular System

THC travels around the body within seconds to minutes after smoking, causing a significant heart rate spike lasting for several hours. Cannabis dilates blood vessels – responsible for the associated bloodshot eyes – and makes the heart pump faster, putting users at increased risk of heart attacks and other cardiovascular conditions. 

Damage to Adolescent Brain Development

Young people who use marijuana have a higher risk of having issues related to brain development. Marijuana use in adolescence can cause irregularities in brain areas that regulate executive functions and decision-making. The extent to which marijuana may impair the teenage brain is still the subject of research, but they may experience memory loss, diminished problem-solving ability, and concentration issues later in life. 

Memory Issues and Decreased Cognitive Function

One of the most concerning side effects of THC is that it binds to areas of the brain that control learning, memory, and other cognitive functions. Consequently, users can suffer long-term impairment of these functions in the short term, which may worsen in the long term with continued regular use.

Cannabinoid Hyperemesis Syndrome (CHS)

Cannabinoid Hyperemesis Syndrome (CHS) is a condition characterized by severe and repeated bouts of vomiting caused by regular and long-term cannabis use. People with CHS may also experience dehydration and abdominal cramps. Though a rare condition only experienced by daily long-term users, it can be pretty unpleasant and lead to digestive system changes. 

Anxiety and Depression

Marijuana helps users feel relaxed, but high levels of THC can increase users’ anxiety levels. People with anxiety disorders may see their anxiety levels increase with prolonged marijuana use. Marijuana users also get diagnosed with depression at a higher rate than those who do not. The connection between marijuana and depression is unclear, but those who use marijuana to cope with depression may see their condition worsen, even if it improves initially.

Psychosis and Other Psychiatric Disorders

Some research suggests that there may be a connection between weed use and psychosis or other psychiatric conditions. Users of high-potency THC may be up to five times more likely to develop a psychotic disorder. Individuals with a family history of psychiatric disorders should avoid cannabis as it could significantly increase their chances of developing mental health problems. 

Pregnancy and Breastfeeding-Related Risks

Marijuana use during pregnancy can harm the baby’s health and lead to developmental issues, preterm birth, and stillbirth. THC and other toxic compounds present in cannabis can pass from the placenta to the baby, causing various complications. THC is also detectable in breast milk and can remain for up to six weeks. The impact of cannabis on nursing infants is unclear, but nursing mothers are encouraged to avoid marijuana. Those who use cannabis for medical reasons should consider alternative therapies during breastfeeding. 

Decreased Production of Testosterone

Potent strains of THC can cause side effects such as diminishing the body’s ability to produce testosterone, which can lead to erectile dysfunction, lack of energy, weight gain, low libido, and reduced mental clarity. A study shows that a single marijuana joint can make testosterone levels drop for at least 24 hours, though it may return to normal if use is discontinued. 

Testicular Cancer

Emerging studies suggest that men who used cannabis for longer than ten years were 50% more likely to develop testicular cancer than those who never used cannabis. Another study provided some evidence that cannabis smokers were 36% more likely to develop testicular cancer. 

Additional Substance Use Disorders

Marijuana is considered by many as a gateway drug; this means that it provides a relatively safe psychoactive experience that makes naïve users more open to experimenting with more potent substances. People with additional substance use disorders often have prior experience with marijuana. Marijuana use doesn’t always translate to abuse of other drugs, but the brain changes associated with THC increase one’s likelihood of developing additional substance use disorders. 

Benefits of Marijuana Use

Marijuana has been used to treat several ailments with varying degrees of success for centuries. The medical community agrees that marijuana use has multiple health benefits, including: 

Pain Relief

Cannabinoids alter how we perceive pain, making them helpful in treating conditions that cause chronic pain, such as arthritis, migraine, endometriosis, and fibromyalgia. Medical marijuana may replace Non-Steroidal Anti-inflammatory Drugs (NSAIDs) like ibuprofen and diclofenac, which have side effects with long-term use. 

Reducing Inflammation

Studies show that cannabidiol (CBD), the non-psychoactive constituent of cannabis, can help reduce inflammation, making it potentially useful for conditions like Crohn’s disease, ulcerative colitis, and irritable bowel syndrome (IBD).

Improved Sleep

Marijuana brings relaxation, which may make it helpful in treating insomnia and other sleep disorders. The pain relief from cannabis use can also lead to improved sleep quality. 

Multiple Sclerosis Management

People with multiple sclerosis may experience improved spasticity symptoms with short-term cannabinoid use. 

Treating Anxiety

CBD is probably used for treating anxiety more than any other ailment. Studies show it may effectively treat social anxiety, obsessive-compulsive disorder, panic disorder, and post-traumatic stress disorder. 

Epileptic Seizures

Studies show that CBD has positive outcomes when treating epilepsy and other types of seizures. Epidiolex is a CBD-based drug approved for treating Dravet’s Syndrome and Lennox-Gastaut Syndrome – two rare types of epileptic conditions that do not respond to conventional medications.

Cancer Treatment

CBD is useful for treating nausea and vomiting associated with chemotherapy, while some evidence suggests that marijuana may slow the growth or induce death of cervical cancer cells.


Weed use remains one of the most divisive topics among health experts and legislators. The negative effects of weed use are apparent, but there’s no denying that cannabis may provide significant health benefits. However, it’s essential to seek a professional’s opinion before using marijuana to treat any condition. Depending on where you live, you may also need legal guidance on obtaining and using marijuana. 

If you or a loved one is abusing or addicted to marijuana, the Canadian Centre for Addictions can help. At CCFA, our team of addiction experts combines over 100 years of experience in dealing with weed addiction, withdrawal, and related issues. We are a rehab that provides the help and support you or your loved one need to understand and overcome their condition. Visit our Understanding Addiction Resources for information on marijuana addiction and what we do.

Frequently asked questions

Is smoking weed more harmful than cigarettes?

All types of smoking are harmful, but smoking weed may cause more harm than cigarettes because weed smokers tend to inhale deeply and hold their breath for longer before exhaling, so they are more exposed to tar and other toxins from smoke.

Does weed make you gain weight?

Weed use is associated with increased appetite, known as the “munchies,” but studies vary on whether this leads to overall weight gain. While weed use seems to affect weight, it is unclear whether it causes weight gain or loss. Both outcomes may be possible with weed use, depending on the user.

Can smoking weed cause a miscarriage?

Yes. When pregnant women smoke weed, THC and other chemicals can pass from the placenta to the baby, leading to potential problems like preterm birth, stillbirth, and other developmental issues.

Is CBD a depressant or a stimulant?

CBD is neither a depressant nor a stimulant. However, the chemical elicits stimulant or depressant effects depending on the dosage. It is biphasic; higher doses decrease blood pressure and may cause depressive effects, while lower doses enhance focus and alertness.

Does weed make you introspective?

The high that comes from marijuana use might have several effects on one’s mind and could be responsible for the mental enhancements described by users. The plant’s potential to cause introspection and reflective thinking may be the basis for the religious use of the plant.

Can quitting weed raise blood pressure?

Yes. Abrupt cessation of weed use may cause significant blood pressure elevation in chronic, heavy users. Blood pressure monitoring is required for individuals attempting to quit cannabis, especially those with pre-existing hypertension.

Certified Addiction Counsellor

Seth brings many years of professional experience working the front lines of addiction in both the government and privatized sectors.

Dr. Chintan is a Board Certified Family Physician with an interest in holistic and preventative care as well as healthcare systems. Credentialed Physician with both American & Canadian Board of Family Medicine. Adjunct Professor in the Department of Family Medicine at the Schulich School of Medicine & Dentistry. Telemedicine clinician.

More in this category: