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Mental Health Effects of Marijuana

Rob Orman, MD and Shawn Hersevoort, MD, MPH

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Marijuana use is an emerging area of research in mental health. It has been linked to increased risk of psychosis in vulnerable individuals, paranoia, amotivation syndrome, and IQ loss. Many patients use it to self-treat anxiety and depression symptoms.  Currently, there is not enough evidence to support its use as a mainstream treatment for mental health disorders.



  • There is ample evidence to support marijuana (MJ)  as  treatment for nausea and appetite stimulation. Research is also emerging around headache, chronic pain and insomnia.

  • MJ users have an increased risk of psychosis, especially in those with a family history of psychotic disorders.

  • MJ use decreased IQ in youth by 5-10 points who regularly smoke it 1-2 times per week.

  • MJ use can create paranoia and anxiety, though patients often use it to self-treat mood disorders.


  • Where does MJ have ample evidence to support its use? Nausea, appetite stimulant. Encouraging evidence around headache, chronic pain, and insomnia.

  • Where does MJ use get complicated? Mood disorders, among other areas. If you feel depressed all day and you’re smoking pot all day, try cutting down on the pot to see if it helps with your symptoms.

    • Anxiety: common side effect is paranoia or anxiety but in other people it can be calming. However, just because while intoxicated with MJ you are calm doesn’t mean you are functioning better. Withdrawal may then induce the opposite state, leaving patient caught in a loop.

  • Other things to look for in patients using MJ regularly? Amotivational syndrome, IQ loss in  people under the age of 20, and increased risk of psychosis.

    • Daily use demonstrates decrease in functionality and quality of life in the long run.

    • One percent across the board increased risk in psychosis both young and old (ie: schizophrenia, schizoaffective disease, dementia with psychosis). MJ is also thought to induce or unmask underlying psychotic disorders that may clear after weeks or months or persist. Those with a family history of psychosis are particularly at risk.

    • Youth under age  20 lose 5-10 IQ points with as low as twice a week ongoing MJ use. This is a critical time of brain development where the brain is pruning high centers, math centers and focus centers.

    • MJ use is also associated with amotivational syndrome.

  • Is there a role for treating mood disorders with MJ? This an area of active research.  Dr. Hersevoort believes that when the evidence is there “then everything will align...the FDA will get behind it and everyone will agree on the risks/benefits/alternatives”. In the meantime , if someone has been using it to self-treat and they believe it helps them without causing harm, Dr. Hersevoort suggests a fair response is to give your recommendation and let them choose.

Bottomline: MJ is a powerful neurochemical substance that can cause addiction and withdrawal. We don’t  yet fully know the long term effects.

Paul B. -

Interesting discussion as Medical Cannabis is becoming very topical in local medical and lay media - Queensland Australia. Many of the GP/Primary Care Practitioners are trying to get there head around this.

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Sweat Puddled, Brains Muddled Full episode audio for MD edition 173:58 min - 82 MB - M4AHippo Primary Care RAP February 2017 Summary 316 KB - PDF