Medical Disclaimer: This information is educational only and does not constitute medical advice. Cannabis affects everyone differently. Always consult a qualified healthcare provider before using cannabis, especially if you take other medications. Never discontinue prescribed medications without medical supervision.

Honest Risk Assessment

One of the most important things a credible cannabis resource can do is tell you clearly when cannabis may not be right for you. The groups listed on this page should either avoid cannabis entirely or exercise extreme caution with direct medical supervision.

This is not about being anti-cannabis. It is about being pro-safety. If any of the categories below apply to you, please read the relevant section carefully and discuss it with your healthcare provider before using cannabis in any form.

Anyone Under 21: Brain Development

The human brain continues developing until approximately age 25, with the prefrontal cortex — responsible for decision-making, impulse control, and complex reasoning — being one of the last regions to fully mature. Cannabis use during this critical developmental window has been associated with adverse cognitive and psychiatric outcomes.

What the Research Shows

Cognitive effects: Regular cannabis use during adolescence and early adulthood has been associated with measurable changes in attention, memory, processing speed, and executive function. Some studies suggest these effects may persist even after cessation of use, though the degree of reversibility remains debated.
Psychiatric risk: High-potency cannabis use in adolescents has been associated with higher rates of generalized anxiety disorder — 19.1% compared to 11.6% for low-potency cannabis. The risk of psychotic disorders, including schizophrenia, is also elevated in young users, particularly those with genetic predisposition.
Structural brain changes: Neuroimaging studies have identified differences in brain structure and connectivity in adolescent cannabis users compared to non-users, particularly in areas related to memory (hippocampus) and executive function (prefrontal cortex).

Why we set the threshold at 21: All information on TryCannabis.org is intended exclusively for adults aged 21 and older. While some states allow medical cannabis access for patients aged 18 to 20 with qualifying conditions, the brain development evidence strongly supports waiting as long as possible. The older you are when you begin using cannabis, the lower your risk of adverse developmental effects.

Pregnant or Breastfeeding Individuals

There is no established safe level of cannabis use during pregnancy or breastfeeding. This is one of the clearest contraindications in cannabis medicine, and it applies to all forms of cannabis — smoked, vaped, edibles, topicals, and CBD products.

Why This Matters

THC crosses the placenta. When a pregnant person uses cannabis, THC reaches the developing fetus. The endocannabinoid system plays a critical role in fetal brain development, and external cannabinoids may disrupt this process.
THC is present in breast milk. Studies have detected THC in breast milk for up to six days after use. Infants' developing brains are particularly vulnerable to cannabinoid exposure.
Associated risks: Cannabis use during pregnancy has been associated with lower birth weight, preterm birth, and potential neurodevelopmental effects in children. While the research is still evolving, the precautionary principle strongly applies here.

Despite increasing social acceptance of cannabis, all major medical organizations — including the American College of Obstetricians and Gynecologists (ACOG), the American Academy of Pediatrics (AAP), and the FDA — recommend against cannabis use during pregnancy and breastfeeding.

If you are using cannabis for nausea during pregnancy: Morning sickness can be severe, and we understand the desire for relief. However, there are FDA-approved treatments for pregnancy-related nausea that have been studied for safety in pregnant populations. Please discuss alternatives with your obstetrician rather than self-treating with cannabis.

For a detailed exploration of this topic, visit our Pregnancy & Breastfeeding page.

Personal or Family History of Psychotic Disorders

People with a personal or family history of schizophrenia, schizoaffective disorder, or other psychotic disorders should avoid cannabis — particularly high-THC products. This is one of the most well-established risk associations in cannabis research.

The Evidence

Triggering psychotic episodes: Cannabis, particularly high-THC products, can trigger acute psychotic symptoms in people who are predisposed. For individuals with existing psychotic disorders, cannabis use can worsen symptoms and interfere with treatment.
Earlier onset: Research suggests that cannabis use in genetically predisposed individuals may accelerate the onset of psychotic disorders by several years.
Dose-response relationship: The risk appears to be dose-dependent. High-potency cannabis and frequent use carry greater risk than occasional use of lower-potency products. However, for individuals with strong genetic predisposition, even moderate use may be problematic.
Family history matters: Even if you have never personally experienced psychotic symptoms, a first-degree relative (parent, sibling) with a psychotic disorder significantly increases your risk. Cannabis may be the environmental trigger that activates an underlying genetic vulnerability.

This is not subtle: If you have been diagnosed with or have a close family history of schizophrenia or schizoaffective disorder, the consensus in psychiatric medicine is clear — cannabis use is strongly contraindicated. This is not an area where "starting low" mitigates the risk sufficiently. Please discuss this with your psychiatrist.

For more on this topic, visit our Mental Health Considerations page.

Certain Cardiovascular Conditions

If you have a history of heart disease, heart attack, stroke, arrhythmia, or other cardiovascular conditions, cannabis use requires extreme caution and direct medical supervision.

The 2025 JAMA review noted that daily use of cannabis, particularly inhaled or high-potency products, may be associated with elevated risks of coronary heart disease, heart attack, and stroke.
Hsu et al., JAMA / UCLA Health, 2025

How Cannabis Affects the Cardiovascular System

Heart rate: THC can increase heart rate (tachycardia), sometimes by 20 to 50 beats per minute. For healthy adults, this is usually benign and temporary. For people with heart conditions, it can be dangerous.
Blood pressure: Cannabis can cause an initial increase in blood pressure followed by a decrease. This rapid fluctuation can be problematic for people with blood pressure disorders or those taking blood pressure medications.
Inhalation risks: Smoking cannabis introduces combustion byproducts that can stress the cardiovascular system, independent of the cannabinoids themselves. Vaporization reduces but does not eliminate these concerns.

If you have a cardiovascular condition and still wish to explore cannabis, this conversation must involve your cardiologist. Non-inhaled, low-dose methods (such as sublingual tinctures or low-dose edibles) may carry less cardiovascular risk than smoking, but this is a decision for your doctor to help you make.

For a deeper dive, visit our Cardiovascular Risks page.

History of Substance Use Disorder

This category requires nuance. A history of substance use disorder (SUD) does not automatically disqualify someone from using medicinal cannabis, but it does warrant honest self-assessment and medical guidance.

Approximately 29% of medical cannabis users met criteria for cannabis use disorder in one major review. Risk factors include daily use, use of high-potency products, younger age of initiation, and using cannabis to cope with negative emotions.
Hsu et al., JAMA, 2025

The Nuanced Reality

Cannabis can be addictive. Cannabis use disorder (CUD) is a recognized clinical diagnosis. While the physical dependence potential is lower than substances like alcohol, opioids, or benzodiazepines, psychological dependence is real and can significantly impact quality of life.
People with prior SUD are at elevated risk. If you have struggled with alcohol, opioids, stimulants, or other substances, you may be more susceptible to developing problematic cannabis use patterns. This is not a moral failing — it reflects neurobiological factors related to reward circuitry.
However, context matters. Some research suggests that cannabis may help certain individuals reduce dependence on more harmful substances, particularly opioids. The evidence for opioid dose reduction in supervised medical settings is growing. This is a fundamentally different scenario from unsupervised recreational use.
The key distinction: Using cannabis under medical supervision, with clear therapeutic goals and regular monitoring, is very different from self-medicating without accountability. If you have a history of SUD, the former is essential.

Questions to ask yourself honestly: Am I considering cannabis for a genuine medical need, or am I looking for a new way to escape uncomfortable emotions? Do I have a history of losing control with substances? Am I willing to set strict boundaries around my use and involve a healthcare provider in monitoring? If the answers give you pause, talk to an addiction specialist or therapist before proceeding.

For more on recognizing and addressing problematic use, visit our Cannabis Use Disorder page.

Anyone in Impairment-Sensitive Situations

Beyond the medical contraindications above, cannabis should never be used by anyone who is about to operate a vehicle, heavy machinery, or engage in activities that require full cognitive and motor function.

Driving: THC impairs driving ability. A 2025 analysis found that over 40% of drivers killed in fatal crashes had THC in their blood far above legal limits. Cannabis impairment is a DUI offense in all states.
Workplace safety: If your job involves operating equipment, working at heights, or making safety-critical decisions, cannabis use before or during work is dangerous and likely a violation of workplace policy.
Caregiving: If you are the sole caregiver for children or dependent adults, plan your cannabis use for times when another responsible adult is available, particularly while you are still learning how cannabis affects you personally.

For detailed guidance on wait times and impairment awareness, visit our Driving & Impairment page.

Summary: Should You Use Cannabis?

The following table provides a quick reference. It is not a substitute for a conversation with your healthcare provider.

Group	Recommendation
Under 21	Avoid. Brain is still developing. Risk of cognitive and psychiatric effects.
Pregnant or breastfeeding	Avoid. No established safe level. All major medical organizations advise against it.
Personal/family history of psychotic disorders	Avoid. Can trigger or worsen psychotic symptoms. Consult psychiatrist.
Cardiovascular conditions	Extreme caution. Discuss with cardiologist. Avoid inhalation methods.
History of substance use disorder	Caution with medical supervision. Honest self-assessment required. Involve your doctor.
Before driving or operating machinery	Never. Wait at minimum 4–6 hours after inhalation, 6–8 hours after edibles.

If none of these categories apply to you, cannabis may still carry risks — particularly if you take other medications. Before using cannabis for any purpose, read our Drug Interactions page and have an honest conversation with your healthcare provider. Safety is not about avoiding cannabis — it is about using it wisely.

Are You 21 or Older?

Who Should NOT Use Cannabis