Marijuana Use: The Good, the Bad, and the Unknown

Cannabis Use in the US

The use of cannabis continues to increase across the US, across all age groups, and both genders, with people aged 18-25 using it at the highest rate.¹ Whether individuals are using these products for medical or recreational purposes, both patients and healthcare professionals need to understand their effects and potential risks.

Cannabis, THC, CBD, Marijuana, and Hemp

The flowering plant Cannabis sativa contains about 540 chemical substances, including tetrahydrocannabinol (THC), which is the intoxicating compound, and cannabidiol (CBD).² Not all plants of the species are the same, and different cultivars have different amounts of THC and CBD.

By law, if a Cannabis sativa plant has ≥0.3% of THC by dry weight, it is considered ‘Cannabis.’³ This is the type of plant used to create medicinal and recreational products. If a Cannabis sativa plant contains ≤0.3% of THC by dry weight, it is considered to be hemp.³ These plants are typically used for fibers for clothing and other products.

The Legality of Cannabis

As of June 2025, 48 states, the District of Columbia, and 3 US territories have approved the use of cannabis for medical purposes, while 24 states have legalized products for recreational use.⁴ Laws governing use in each state may vary widely, including limits to the amount of THC and CBD in strains of marijuana and related products.

In December 2025, a Presidential Executive Order was signed to reclassify marijuana to a Schedule III drug, in the same category as other drugs used medically, including ketamine and anabolic steroids.⁵ As of the time of this article, marijuana is still considered a controlled substance subject to rules and regulations. The Executive Order does not provide an outright legalization of marijuana for recreational use, but allows for greater research about the drug to investigate benefits, potential dangers, and future treatments.⁴ The process to reschedule may take many months, so it is important to check on the latest legal requirements and guidance.

Potency of Marijuana Products

THC and CBD levels vary from one marijuana strain to another. There are also differences in effects based on the delivery system, whether inhaled (smoking or vaping) or ingested. Some edibles may contain just THC, just CBD, or a combination of both, further complicating the measure of potential effects.

Legal cannabis products sold in the US are required to report THC potency (the total THC percentage by dry weight). If you’ve heard that potency has increased over time, that is not a fallacy. Research demonstrates that average potency was around 1-4% in the 1960s, <4% in the 1990s, and in the early 2020s, potency had risen to more than 16%.⁶

This increase in potency may lead to individuals ingesting more THC than intended—especially older adults. Studies in California and Canadavi demonstrate that cannabis-related trips to the ER for those over 65 have skyrocketed—sometimes by more than 1,800%.⁷

Potential Positive Impacts

So, how does marijuana affect the body? Research continues to improve our understanding of the health effects of THC and marijuana products, but there are a variety of impacts that can affect our patients.

It is critically important to weigh all the impacts of cannabinoids (the active ingredient in cannabis) and use shared decision-making in conversations with patients who are considering, or already using, these products. Responsible use under guidance is crucial.

Many people choose to use THC and CBD products to treat chronic pain, calm muscle spasms caused by multiple sclerosis, help increase hunger in health conditions that cause low appetite, or ease nausea as a result of chemotherapy.

Ongoing studies are assessing if cannabis works better than other options to manage pain, and a few studies have found that neuropathic pain can be reduced with use.⁸ With more than 20% of US adults with chronic pain according to CDC estimates, THC and CBD products are often sought as alternatives to opioids or long-term use of NSAIDs for pain management.⁹

There are, however, potential health risks to using cannabis. Some of these are identified below.

Detrimental Health Impacts of Marijuana

Cardiovascular Disease

Using cannabis increases both heart rate and blood pressure. Cannabis use has strong, statistically significant associations with adverse cardiovascular outcomes and may be a risk factor for CVD, including premature CVD,¹⁰ coronary heart disease, stroke, and STEMI.¹¹

Brain Function and Mental Health

Cannabis use directly affects brain function, particularly related to decision-making, coordination, memory, learning, attention, emotions, and reaction time.¹² Heavy lifetime cannabis use was associated with lower brain activation in working memory tasks, indicating that short- and long-term brain function is impacted.¹³

Researchers are still investigating the relationships between cannabis and mental health issues, and cannabis use has been linked to depression, social anxiety, and schizophrenia.⁸

About 1 in 10 people will become addicted to marijuana; for those who start use before the age of 18 the rate rises to 1 in 6.1 Cannabis use disorder affects approximately 3 in 10 users.¹⁴

Lung Function

No matter how it is inhaled (smoking or vaping), cannabis can harm lung tissues. It may also cause scarring and damage to small blood vessels.⁸

Diabetes

A recent study (an unpublished abstract) indicates that people who use cannabis may have a 3.7 times greater risk of type 2 diabetes compared to the general population.¹⁵ The study of medical data from more than 95,000 cannabis-using adults in the US and Europe only showed an association, not whether the use of cannabis leads to the development of diabetes. Researchers suggested that cannabis may contribute to type 2 diabetes through endocannabinoid system overstimulation, which promotes visceral adiposity, hepatic fat accumulation, and insulin resistance.

It also may contribute to low-grade inflammation, oxidative stress, and potential beta-cell dysfunction, which impair glucose homeostasis. Other considerations may be poor eating habits, including overeating, as a result of cannabis use.

Fetal Health and Development

Use of marijuana during pregnancy may cause restriction of fetal growth, premature birth, stillbirth, and issues with brain development, which can lead to hyperactivity and poor cognitive function.¹ THC and other chemicals can not only cross the placental barrier but also be passed on through breast milk.

Clinical Takeaways

• Check at every visit for use of cannabis and other substances, including frequency and duration of use. This can be done as part of check-in screening, rooming, or as part of the clinical discussion.
• Be mindful of terms to minimize patient anxiety. For example, instead of terms such as ‘illegal’ or ‘illicit’ drugs, use the term ‘recreational.’
• Be specific about what you are asking. Rather than just ‘Do you use cannabis products?’ ask ‘How often do you use cannabis products? Daily? Weekly? Monthly? Yearly?’
• Ensure that discussions with patients about topics such as medical or recreational use of cannabis products are handled in a nonjudgmental, compassionate way. This ensures that patients are more comfortable sharing sensitive information that may affect their health and treatment options.
• During your discussion, be mindful of nonverbal cues such as facial language and body posture, as well as tone of voice, to encourage honesty.
• Work to identify the ‘why’ behind the use of cannabis. Is it medical? Social? Are there other alternatives that may be available that you can suggest?
• Use a shared decision-making process for the discussions. Where possible, use decision tools and patient education resources to support options, provide take-home resources, and encourage ongoing adherence to decisions.