Marijuana
Cannabis (marijuana, or weed) is one of the most commonly used recreational substances, and its legal status is changing rapidly. But what are the actual risks? The truth is, the risk isn't the same for everyone. It depends heavily on who you are, how you use it, and how often.
This page is an interactive tool to help you explore the science-based risks. Use the choices below to match your own situation, and the risk models will update to show you estimates based on data from major public health institutions.
Your Choices
To see your personalized risk estimates, please make a selection from each category below. The risk displays will appear once all the required factors have been chosen.
How do you typically use it?
How often do you use it?
What is your age group?
Your Estimated Risks
Baseline Factors
Method of Consumption
| Method_Description | Method_IsSmoked | Method_IsVaped | Method_IsEdible |
|---|---|---|---|
|
Smoking (joint, pipe, bong) |
1 |
0 |
0 |
|
Vaping (flower or oil) |
0 |
1 |
0 |
|
Edibles (gummies, baked goods, drinks) |
0 |
0 |
1 |
This choice determines which risks are relevant. Smoking and vaping carry respiratory risks that edibles do not.
Frequency of Consumption
| Frequency_Description | Frequency_CUD_Multiplier | Bronchitis_Smoking_Pct | Bronchitis_Vaping_Pct |
|---|---|---|---|
|
Rarely (a few times per year) |
1 |
4 |
3 |
|
Occasionally (1-3 times per month) |
2 |
7 |
5 |
|
Regularly (1-3 times per week) |
4 |
12 |
8 |
|
Daily or Near-Daily |
5.5 |
19 |
12 |
This data provides multipliers for Cannabis Use Disorder based on frequency of use, and estimated prevalence of chronic bronchitis symptoms for smokers and vapers.
The bronchitis prevalence values are interpolated from Aldington et al. (2007), which found 2.5% prevalence in non-users and 18.7% in regular cannabis smokers (mean 54 joint-years). Intermediate values are estimated based on dose-response patterns observed in longitudinal studies. Vaping prevalence estimates are lower based on limited comparative data suggesting reduced respiratory impact compared to smoking.
- Adverse Health Effects of Marijuana Use | New England Journal of Medicine (CUD Risk)
- Effects of cannabis on pulmonary structure, function and symptoms | Thorax (Aldington et al., 2007 - Bronchitis prevalence)
- Effects of quitting cannabis on respiratory symptoms | Thorax (Hancox et al., 2015 - Dose-response)
Your Age
| Age_Description | Age_CUD_Multiplier | Age_Cognition_Impact |
|---|---|---|
|
Under 18 |
4 |
High |
|
18-25 |
1.5 |
Moderate |
|
26+ |
1 |
Low |
This data provides a risk multiplier based on age, primarily for CUD and long-term cognitive effects. The adolescent brain (<18) is significantly more vulnerable to the effects of THC.
Risk Models
RiskModel: Marijuana:DrivingRisk Content: ===Short-Term Risk: Impaired Driving=== When driving under the influence of cannabis, your risk of a motor vehicle crash is approximately '''doubled'''.
Calculation: This is a general finding from numerous meta-analyses. The average relative risk for a motor vehicle crash after cannabis use is consistently found to be around 2.0.
- The Health Effects of Cannabis and Cannabinoids: The National Academies of Sciences, Engineering, and Medicine (See Chapter 13)
RiskModel: Marijuana:CUDRisk
Content:
===Long-Term Risk: Moderate or Severe CUD (Addiction)===
Based on your age and frequency of use, your lifetime risk of developing a '''Moderate or Severe''' Cannabis Use Disorder (addiction) is about {{One_In_X|{{#expr: 0.02 * {Frequency_CUD_Multiplier} * {Age_CUD_Multiplier} }} }}.
Calculation: This model estimates the risk of a Moderate or Severe CUD (4 or more DSM-5 symptoms), which better reflects a life-impairing disorder. The model starts with a baseline risk of 2% (1 in 50) for a rare, adult user. This risk is then multiplied by factors for frequency of use and age of onset. The risk is highest for young, daily users.
- Is Marijuana Addictive? | NIDA
- 2020 National Survey on Drug Use and Health | SAMHSA (See Table B.4B for severity breakdown)
RiskModel: Marijuana:BronchitisRisk
Content:
===Long-Term Risk: Chronic Bronchitis Symptoms===
{{#ifexpr: {Method_IsSmoked} = 1
|Based on your frequency of smoking, your estimated prevalence of chronic bronchitis symptoms is '''{{One_In_X|{{#expr: {Bronchitis_Smoking_Pct} / 100 }} }}'''. For comparison, the baseline rate in non-smokers is about '''1 in 40''' (2.5%).
|{{#ifexpr: {Method_IsVaped} = 1
|Based on your frequency of vaping, your estimated prevalence of chronic bronchitis symptoms is '''{{One_In_X|{{#expr: {Bronchitis_Vaping_Pct} / 100 }} }}'''. For comparison, the baseline rate in non-smokers is about '''1 in 40''' (2.5%). Note: Long-term vaping data is limited.
|This risk is not associated with edibles.
}}}}
Calculation: Prevalence estimates are based on Aldington et al. (2007), which compared 75 cannabis-only smokers to 81 non-smokers in New Zealand. Non-smokers had 2.5% prevalence of chronic bronchitis symptoms; cannabis smokers had 18.7%. Intermediate frequency values are interpolated based on dose-response patterns. Vaping estimates are reduced based on preliminary evidence suggesting lower respiratory impact, though long-term data remains limited. Notably, symptoms often resolve after quitting or reducing use.
- Effects of cannabis on pulmonary structure, function and symptoms | Thorax (Aldington et al., 2007)
- Effects of quitting cannabis on respiratory symptoms | Thorax (Hancox et al., 2015)
Initially created by Gemini.