Marijuana: Be informed

You have the right to make your own decisions. Our goal is to ensure you have the most accurate and reliable information to make the best decisions possible for yourself.

Basic chemistry

Marijuana’s main psychoactive chemical is delta-9-tetrahydro-cannabinol, commonly known as THC. Due to the variety of strains, potency, and the effects it can produce, marijuana can be categorized as a depressant, a hallucinogen, or a stimulant, making it difficult to predict how individuals may react.

Here are the generally accepted short-term physiological effects of each drug class:

  • Depressants make individuals feel tired, slow, relaxed, unfocused, uncoordinated and unable to think clearly.
  • Hallucinogens may cause abnormal visual or auditory experiences, unusual thoughts, or altered awareness.
  • Stimulants can lead to anxiety, agitation, and increased heart rate.

Persistent effects of marijuana use

New research continues to evolve our knowledge about the effects of marijuana and THC.

Cognitive effects and mental health

Marijuana use can affect attention, concentration, and short-term memory. For students with a diagnosis of ADD or ADHD, using marijuana worsens these pre-existing attention difficulties. New research suggests that marijuana’s effects can last up to three days after use. These persistent effects (sometimes called “pot hangovers”) can include impaired memory and learning skills and a decrease in alertness, coordination, and depth perception.

Heavier marijuana users have higher deficits in these areas than those who use at lower levels. The cognitive effects of marijuana may vary by age. In research with adults, most cognitive deficits related to marijuana use seem to be temporary, with improvement after several weeks of abstinence. However, new research on adolescents between ages 15-19 shows that it may take longer for the adolescent brain to recover from deficits related to marijuana use, particular when it comes to attention.

Marijuana can lead to increased anxiety, depression, and schizophrenia in individuals who are predisposed to developing mental illness. For those with a history of anxiety or depression, marijuana use can worsen these symptoms. While some people report that using marijuana helps alleviate anxiety or depression in the short term, it can contribute to a long-term worsening of symptoms and reliance on marijuana as a coping mechanism to manage the anxiety and/or depression.

Physical effects

Marijuana raises the resting heart rate by 29 beats per minute and increases blood pressure. For those with pre-existing heart conditions, heart disease, or a diagnosis of anxiety, smoking marijuana can be particularly unsafe.

Driving. Researchers are investigating the development of a per se limit as it relates to impairment from marijuana use much in the way that we have the .08 threshold in Massachusetts for alcohol. Know that there is a risk when it comes to driving under the influence of marijuana and that this risk appears to be present for a minimum of five-six hours after smoking.

Addictive potential & withdrawal symptoms

Heavy marijuana use can lead to dependence. “A quarter to a half of those who use marijuana daily are addicted to the drug.” (NIDA, 2010)

Withdrawal symptoms from marijuana include: irritability, sleeplessness, decreased appetite, anxiety, and drug craving. These symptoms begin about one day following abstinence, peak at 2-3 days, and subside within 1-2 weeks following cessation.

Sleep-related effects

While some individuals find that marijuana helps with falling asleep, it actually prevents the necessary rest and deep sleep the body requires during the remainder of the sleep cycle. Marijuana reduces REM (rapid eye movement) sleep—the type of sleep that allows people to feel rested and alert after waking up. Adequate REM sleep is also required for the development of long-term memory as well as muscle rebuilding and repair. Effects can last for several days after marijuana use and create disruption in the body’s natural sleep rhythm.

For more information and a list of references, check out our Marijuana fact sheet.