Thinking about using cannabis (or "weed") for health reasons? This guide will help you understand what it might do, what to watch out for, and how to make smart choices.

Important Note: While some people find cannabis helpful, it's not a magic cure-all. The way it affects you can be very different depending on the type, how much you use, and your own body. Also, there aren't always strict rules about how these products are made, so it's good to be careful.

Use our Decision Maker to help decide if medical cannabis is right for you

What Might Cannabis (Weed) Help With?

People use cannabis for a bunch of different reasons. Here are some of the main ones:

• Pain Relief:

• Nerve Pain: Some studies show it can help with pain from damaged nerves, like a tingling or burning feeling. Products with more THC (the part that gets you high) or a mix of THC and CBD (the part that doesn't get you high) seem to be useful.
• Muscle & Joint Pain: People with conditions like arthritis or fibromyalgia sometimes say cannabis helps with their pain and makes it easier to move, possibly because it can reduce swelling.
• Overall Chronic Pain: Many use it for long-lasting pain, and some find it helps them use less strong pain medicines, even opioids.

• Cancer-Related Issues:

• Pain: It can help manage pain for cancer patients and might reduce the need for other pain meds.
• Nausea & Vomiting: Certain cannabis-based medicines (especially those with THC) are good at stopping nausea and throwing up from chemotherapy.
• Appetite: THC can give you the "munchies," which can be helpful for cancer patients who need to eat more.
• Feeling Better: It might improve mood, reduce anxiety, and help with sleep for people in palliative care.

• Multiple Sclerosis (MS) Spasms: A specific cannabis-based spray (called nabiximols) has been shown to really help with muscle stiffness and spasms in MS.
• Mental Health (Use with Caution!):

• Anxiety: CBD, which doesn't make you high, might help calm anxiety. Some people with chronic pain or general anxiety have reported feeling better.
• Depression: The evidence here is mixed. While some people use it for depression, it's not a clear solution.
• Sleep Problems: Many people use cannabis to help them sleep better, especially if they have pain.

• HIV-Related Conditions: Some research suggests cannabis might help with swelling and brain function in people with HIV, and it's also used for pain relief.

What Are the Downsides and Risks?

Just like any other substance, cannabis can have side effects and risks.

• Common Side Effects: These are usually mild and go away, especially with THC. They include:

• Dizziness or feeling lightheaded
• Drowsiness or feeling tired
• Dry mouth
• Nausea or upset stomach
• Feeling "high," confused, or having trouble thinking
• Fast heartbeat (less common)

• CBD-Specific Side Effects: If you're mostly using CBD, you might experience:

• Stomach upset (like diarrhea or nausea)
• Drowsiness
• Reduced appetite
• (Rarely, and usually with very high doses) Liver enzyme changes.

• Drug Interactions: Cannabis can affect how other medicines work because your liver processes them similarly. This is especially important if you take blood thinners (like warfarin), certain heart medicines, or some antidepressants. Your doctor needs to know!
• How You Take It Matters:

• Eating/Drinking (Oral): Generally safer for your lungs, but the effects take longer to kick in.
• Inhaling (Smoking/Vaping): Works faster, but might be harder on your lungs over time.

• Addiction Potential:

• If you're using prescribed cannabis at low doses, addiction isn't usually a big concern.
• However, if you use it recreationally, especially high-THC products that are smoked or vaped, there's a higher risk of becoming dependent. CBD products alone don't seem to have addiction risks.

• Product Quality & Regulation:

• Many cannabis products, especially CBD ones, aren't strictly regulated. This means they might not have the amount of CBD or THC they claim, or they could contain harmful chemicals not listed on the label.
• The industry isn't federally regulated, so marketing can be misleading.

• "Wake-and-Bake": Using cannabis within an hour of waking up has been linked to more problematic use, especially for older adults.
• Mixing with Tobacco/Nicotine: Using cannabis with cigarettes or other tobacco products (like in "blunts") can increase health risks.

Who Should Be Careful or Avoid It?

Some people should avoid cannabis or use it with extreme caution:

• Pregnant or Breastfeeding: It's generally advised to avoid cannabis because it could harm the baby's development.
• Younger Adults (Under 25): Your brain is still developing, so cannabis use at this age might increase risks like psychosis or affect your school/work performance.
• Mental Health Conditions: If you have schizophrenia or other psychosis-related disorders, you should not use cannabis.
• Substance Use Issues: If you have a history of drug or alcohol abuse, THC products are generally not recommended.
• Heart Problems: If you have a heart condition (like an irregular heartbeat or coronary artery disease), talk to your doctor. It should be avoided completely if your heart condition isn't stable.
• Liver Problems: While rare at typical doses, high CBD doses can affect your liver.

What Should You Do Before Using?

If you're thinking about trying cannabis for health reasons, here are some smart steps:

1. Talk to Your Doctor: This is the most important step! Your doctor can review your health history, discuss other treatment options, and help you understand how cannabis might interact with any medicines you're already taking.
2. "Go Low and Slow": If you decide to try it, start with a very small dose. Slowly increase it over time until you find what helps your symptoms with the fewest side effects. This helps your body get used to it.
3. Keep a Diary: Write down how much you take, when, and how it affects your symptoms and any side effects. If it's not helping after a few weeks, it might not be the right choice for you.
4. Get Reliable Information: Don't just rely on what you hear from friends or see online. Look for trusted, science-backed sources.

The Bottom Line

Cannabis and its parts (THC and CBD) might offer some relief for certain conditions, especially pain, MS spasms, and some cancer-related symptoms. However, it's really important to be careful. The effects can vary, there are potential side effects and drug interactions, and the products aren't always regulated.

Always talk to a healthcare professional before you start using cannabis for any health reason. They can help you make an informed decision that's best for your health.

How are new vaccines developed and monitored for safety?

New vaccines undergo a rigorous and transparent process through regulatory bodies like the FDA and CDC. Before approval or emergency use authorization, vaccines must complete three phases of clinical trials to ensure safety and efficacy. After authorization, close monitoring continues through surveillance systems such as the "v-safe after vaccination health checker" and VAERS to identify any uncommon adverse reactions or long-term complications that may not have appeared in trials. While side effects are usually mild and temporary, serious reactions are extremely rare.

What is the Vaccine Adverse Event Reporting System (VAERS) and how reliable is its data?

VAERS is a U.S. program co-managed by the CDC and FDA for post-marketing surveillance of vaccine safety. It collects reports of possible harmful side effects after vaccination. While it serves as an "early warning system" to identify potential unforeseen reactions for further study, it has limitations. VAERS relies on public submissions, which can lead to unverified reports, misattribution, underreporting, and inconsistent data quality.

Therefore, raw, unverified data from VAERS is not sufficient to determine cause and effect and should not be used in isolation to draw conclusions about vaccine safety. For example, a report of a vaccine turning someone into the Incredible Hulk was accepted, highlighting the system's openness to unverified claims.

Do vaccines contain harmful ingredients like aluminum or thimerosal?

Vaccines contain tiny amounts of ingredients for specific purposes, and there is no evidence that these ingredients are harmful. Aluminum is used as an adjuvant to boost the immune response to the vaccine; babies receive more aluminum from their daily diet than from vaccines. Thimerosal, a mercury-containing preservative (ethylmercury), was removed from routine Canadian childhood vaccines by the mid-1990s, with only influenza and some hepatitis B vaccines still containing it. No reliable study has found a link between thimerosal in vaccines and developmental disorders, including autism.

How do children's immune responses to vaccines compare to adults, particularly for COVID-19?

Epidemiological evidence suggests children typically have a milder course of disease and reduced mortality from SARS-CoV-2 infection compared to adults. Preliminary data indicate that children may also develop stronger immune responses to COVID-19 vaccines compared to adults. For instance, studies have shown greater antibody responses to the Pfizer-BioNTech COVID-19 vaccine in participants aged 5-15 years than in those aged 16-25 years. This suggests that individualized vaccination strategies for children may be beneficial, potentially involving optimized dosages and intervals, and considering booster doses for older children and adolescents with suboptimal initial responses.

Is there any scientific evidence linking vaccines to autism or other developmental disorders?

No, extensive research consistently shows no link between vaccines and autism or other developmental disorders. Numerous studies, including a landmark Danish study of over 1.2 million children and 23 other studies, have found no connection between vaccination and autism rates. The 1998 study that initially suggested a link between the MMR vaccine and autism has been discredited and retracted by most of its authors due to methodological flaws and selection bias. Leading medical organizations worldwide, including the Canadian Paediatric Society, the Canadian Medical Association, the U.S. Institute of Medicine, and the World Health Organization, affirm there is no connection.

Why are vaccines especially important for older Adults?

As people age, their immune systems naturally weaken, making them more susceptible to severe outcomes from infectious diseases. Vaccines help prepare the body to fight off these infections more quickly, reducing the risk of serious illness, hospitalization, and death. Furthermore, high vaccination rates contribute to community immunity, protecting individuals who cannot be vaccinated or who have weakened immune responses. This is crucial for healthy aging, maintaining independence, and safeguarding public health.

What are some of the key vaccines recommended for older Adults?

Several vaccines are specifically recommended for older Canadians to help maintain their health and independence. These include vaccines for COVID-19, influenza (flu shot), Respiratory Syncytial Virus (RSV, new in 2023), pneumococcal disease (pneumonia), shingles, and tetanus and diphtheria. It's also advised to discuss travel-specific vaccines with a healthcare provider if planning international trips.

Can certain vaccines reduce the risk of dementia?

Recent studies, such as one analyzing the UK Biobank cohort, suggest a potential protective effect of certain vaccines against dementia. Specifically, subjects who received the Zostavax vaccine (for shingles) showed a reduced risk of developing dementia by approximately 20%. While a history of shingles itself was not significantly associated with an increased dementia risk in this study, the vaccination appears to offer a protective benefit. This protective effect might be due to a direct impact of the vaccine or "off-target" effects that influence the immune system and potentially reduce neuroinflammation, which has been implicated in dementia. Further research is needed to understand the causal pathways.

What is an "immunisation stress-related response" (ISRR), and how is it addressed?

Immunization Stress-Related Response (ISRR) is a term introduced by the WHO to describe the spectrum of physical symptoms and signs of a stress response that can occur following immunization. These reactions are not caused by the vaccine itself but are an interplay of the social context of immunization, individual psychological vulnerability, knowledge, and preparedness. Symptoms can range from mild worry and increased heart rate to fainting, anxiety, hyperventilation, and even non-epileptic seizures, particularly when they occur in clusters due to emotional contagion, amplified by social media. Healthcare providers are being trained to recognize and differentiate ISRR from other conditions like anaphylaxis to prevent mismanagement. Effective responses include empathetic communication, addressing individual needs, and transparent communication strategies to counter misinformation and rebuild public trust in vaccination programs.

Why are older adults at a higher risk for serious outcomes from pneumonia and influenza, and how effective are current vaccines?

Older adults are at a significantly higher risk of severe complications, hospitalization, and death from pneumonia and influenza due to a naturally weakening immune system with age. Pneumococcal disease and influenza are leading causes of infection-related mortality in the elderly, with 90% of related deaths occurring in individuals aged 65 and older.

For pneumococcal disease, the 23-valent pneumococcal polysaccharide vaccine (PPSV23) is recommended for adults 65 and older. While effective against invasive pneumococcal disease, its effectiveness in preventing all-cause pneumonia or death in non-institutionalized older adults has been controversial in clinical trials, though some observational studies suggest benefit. Newer pneumococcal conjugate vaccines (like PCV13, PCV15, PCV20) are more immunogenic in the elderly and are being increasingly recommended, with ongoing studies to confirm their broader protective benefits against pneumonia in this age group.

For influenza, annual vaccination is recommended because viral strains change frequently. Observational studies consistently report reductions in all-cause mortality and hospital admissions for vaccinated seniors during flu season. However, the effectiveness of the vaccine can be lower in very elderly individuals (aged 70+) due to immune senescence. Enhanced influenza vaccines (e.g., high-dose or adjuvanted) are recommended for older adults to provide increased benefit. Combined influenza and pneumococcal vaccination can offer an additive preventive effect, reducing the incidence of all-cause pneumonia and death rates in older adults.