Marijuana use linked to schizophrenia, no cancer threat

According to a new report released on Thursday, marijuana use may raise the risk of users developing schizophrenia and other psychoses, but evidence suggests it does not pose an increased threat for cancer.

In the report released by the National Academies of Sciences, Engineering, and Medicine, nearly 100 conclusions on the health effects of marijuana and cannabis-derived products were presented. The survey is one of the most comprehensive studies of recent research in the field and it makes multiple claims regarding the the drug's health impacts.

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"The evidence reviewed by the committee suggests that cannabis use is likely to increase the risk of developing schizophrenia, other psychoses, and social anxiety disorders, and to a lesser extent depression," the report said.

RELATED: Marijuana legalization laws by state

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Marijuana legalization laws by state
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Marijuana legalization laws by state

Alabama: Medical use only, otherwise possession is a felony

(Photo: Dennis Macdonald via Getty Images)

Alaska: Marijuana legalized for medical and recreational use 

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Arizona: Marijuana legalized for medical use

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Arkansas: Medical use only

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California: Legal for medical and recreational use

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Colorado: Legal for medical and recreational use  

(REUTERS/Rick Wilking)

Connecticut: Decriminalized and legalized for medical use 

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Delaware: Decriminalized

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Florida: Medical use only

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Georgia: Medical use only

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Hawaii: Medical use only

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Idaho: Not legal

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Illinois: Decriminalized

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Indiana: Not legal

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Iowa: Medical use only

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Kansas: Not legal

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Kentucky: Not legal

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Louisiana: Medical use only

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Maine: Legal for medical and recreational use

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Maryland: Decriminalized

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Massachusetts: Legal

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Michigan: Medical use only

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Minnesota: Decriminalized

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Mississippi: Decriminalized on first offense

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Missouri: Not legal

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Montana: Medical use only

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Nebraska: Decriminalized on first offense only

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Nevada: Legal

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New Hampshire: Medical use only

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New Jersey: Medical use only

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New Mexico: Medical use only

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New York: Decriminalized unless in public view

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North Carolina: Decriminalized

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North Dakota: Medical use only

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Ohio: Decriminalized

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Oklahoma: Medical use only

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Oregon: Legal for medical and recreational use

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Pennsylvania: Medical use only

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Rhode Island: Decriminalized

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South Carolina: Not legal

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South Dakota: Not legal

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Tennessee: Medical use only

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Texas: Medical use only, decriminalized in Houston and Dallas

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Utah: Not legal 

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Vermont: Decriminalized

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Virginia: Not legal

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Washington: Legal for medical and recreational use

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West Virginia: Medical use only

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Wisconsin: Medical use only

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Wyoming: Not legal 

(Photo: Space Images via Getty Images)

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And while there is evidence suggesting that Marijuana use by individuals with schizophrenia and other psychoses may lead to "better performance on learning and memory tasks," the report also shows a potential link to increased "thoughts of suicide than non-users."

Regarding the link between marijuana and cancer, the committee found evidence that suggests smoking cannabis does not increase the risk for cancers often associated with tobacco use – such as lung and head and neck cancers.

Individuals with bipolar disorder who are near-daily cannabis users show increased symptoms of the disorder than non-users, according to the report.

The evidence under review also suggests that smoking marijuana "on a regular basis" is associated with more frequent chronic bronchitis episodes, chronic cough and phlegm production — but quitting smoking is likely to reduce these conditions. The committee states it is "unclear" whether marijuana use is associated with asthma and other respiratory diseases.

While the committee found impairment in cognitive functions of learning, memory and attention after immediate marijuana use, the report shows limited evidence to suggest that marijuana use correlates to poor academic performance, or has an affect on social relationships. Because most youth begin to experiment with substances in young adulthood and adolescence — age periods when the neural layers fueling cognitive development are most active — there perhaps could be a link between longterm cognitive impairment in those who have stopped smoking marijuana, but the committee found little evidence to suggest these affects exist.

As far as marijuana's effect on newborns, some evidence suggests that smoking during pregnancy is linked to lower birth weights in newborns — but the relationship between the drug and other childhood outcomes is "unclear."

In terms of the therapeutic outcomes of cannabis and cannabinoids which are sometimes used to treat chronic pain in adults, the survey found evidence supporting a "significant reduction in pain symptoms" for patients who were treated with cannabis or cannabinoids.

There is also "substantial evidence" that adults with multiple sclerosis-related muscle spasms who engage in short-term use of certain "oral cannabinoids" improved their reported symptoms.

Christina Gregg contributed to this piece.

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