Kids and teens' brains are still developing, Holland says, which is why they may be more vulnerable to the drug's effects.
People with a family history of mental illness are also at a greater risk for seeing the drug's mind-altering effects. A number of studies have linked chronic marijuana use to increased rates of anxiety, depression and schizophrenia, according to DrugAbuse.gov.
And a more recent study published in The American Journal of Addictions showed an association between adolescent pot smoking and an increase risk of exhibiting anti-social behavior as an adult. The good news is that marijuana has a low rate of addiction; estimates place it at about 9% of users. And as NORML points out, "the consumption of marijuana -- regardless of quantity or potency -- cannot induce a fatal overdose." Many experts say more research is needed to determine the true benefits and long-term side effects of marijuana, whether it's used for medicinal purposes or as a stress reliever.