Even though marijuana is legal, there are still some health risks. Many products that can be used as medicine have harmful side effects. Those effects may be more pronounced depending on how often it is used. There is evidence that regular use of marijuana increases the risk of heart, lung, injury and mental health problems.1 Less is known about health issues that might be caused by infrequent marijuana use. 

What’s inside marijuana?

The active ingredient in marijuana is tetrahydrocannabinol (THC), the chemical that makes you feel “high.” Typical marijuana plants contain more than 400 chemicals, including about 60 that can interact with the body’s nervous system.4 If you smoke marijuana, you might inhale more than 2,000 chemicals.1 Many of those chemicals are similar to the ones in cigarette smoke.10 Marijuana also can be contaminated with mold, insecticides or other chemicals. The health effects of many of these chemicals are still being studied.

Currently retail marijuana is tested for potency and consistency. Other testing for contaminants will be rolled out later in 2015. Some growers and sellers already have started to test their products for contamination. All marijuana products must have labels listing any chemicals that were used during growing or production, and whether or not the product has been tested for contaminants. Products that have not been tested for contaminants must be labeled as “not tested.”

Has the potency of marijuana changed over the years?

Today, marijuana products can be purchased in a variety of concentrations. Some of these products are significantly more potent than the marijuana of the past. Be aware of the concentration you are purchasing or ask before using someone else's product to avoid accidentally consuming too much.