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The Long-Term Side Effects of Marijuana Use

By Jon McKenna
Medically Reviewed by Jennifer Casarella, MD on December 26, 2021
Over time, consistent marijuana use can affect your physical and mental health

Public attitudes toward marijuana have relaxed, and some states have legalized its recreational use for adults 21 and older. But the health impacts from repeated use should not be forgotten. Medical and treatment professionals note a number of long-term side effects.

“The severity of long-term marijuana use depends in large part on the age of the user and the potency of the marijuana being used,” Aaron Weiner, PhD, tells WebMD Conect to Care. He’s a clinical psychologist and addiction counselor in Lake Forest, IL. “The younger someone is when they start using marijuana, and the greater the THC potency, the worse the consequences.”

Troubling Risks

A 2016 article in The New England Journal of Medicine (NEJM) links regular marijuana use during adolescence with a higher likelihood of various long-term effects on the body and mind, including:

Altered brain development: A younger person’s brain can be more vulnerable to adverse long-term effects from THC, which is the primary active ingredient in marijuana. Studies have indicated that adults who smoked marijuana regularly during adolescence have fewer neural fibers in specific brain regions. This can disrupt the brain development process.

School problems: Some experts tie frequent marijuana use to a greater likelihood of dropping out of school. This isn’t to say that marijuana causes this issue, but it can be a risk factor. 

Cognitive impairment: Frequent marijuana use during adolescence has been linked to lower IQs. 

Less satisfaction and achievement: Chronic marijuana use may increase feelings of depression or anxiety. You may feel worse about your life compared to the general population.

The NEJM article also says that long-term or heavy marjuana use can raise anyone’s risk for:

  • Impaired driving ability, which can lead to dangerous car accidents. (This is also a risk of short-term use.)
  • Symptoms of chronic bronchitis, and increased rates of respiratory infections and pneumonia
  • Chronic psychotic disorders, including schizophrenia, in people who are predisposed to them. (Also, experts have linked regular marijuana use to higher risks of anxiety and depression.)

The National Institute on Drug Abuse (NIDA) says regular marijuana use is tied to various other physical symptoms, including:

  • An increased heart rate for up to three hours after smoking, raising risks of heart attack
  • Issues with child development during and after pregnancy
  • Intense nausea and vomiting, a condition known as cannabis hyperemesis syndrome

As for long-term mental issues, the NIDA points to temporary hallucinations and paranoia.

Researchers are finding evidence of a possible link between long-term marijuana use and lung and testicular cancers, notes Eric Lee, MD, a medical director in St. Louis who also runs a telemedicine service offering medical marijuana certifications.

Lee also laments “a very persistent misconception about THC as an adequate treatment for depression” and insomnia, when at best it can be useful to assist an effective main treatment.

Unless you’ve used marijuana long enough to show dramatic personality changes, the long-term effects are usually more subtle and gradual, Weiner says. “It’s easy to miss the symptoms. Someone who knew you at age 15 might say you’re less sharp at age 25, but otherwise the differences do not seem dramatic.” 

Get Help Now

If you or a loved one is struggling with marijuana addiction, WebMD Connect to Care Advisors are standing by to help. The Substance Abuse and Mental Health Services Administration is another resource that may be helpful.

Treatment & Resources for Marijuana Addiction