(Joe Amon, Denver Post file)

Marijuana research: Colorado issues 188-page report on health studies

DENVER — Colorado released a sweeping report Monday about marijuana and health — everything from pot’s effect on drivers, asthma, cancer rates and birth defects.

The 188-page report doesn’t include new research on marijuana. Instead, it’s a review of what its authors call limited existing studies.

The report looks at studies showing that risk of a motor vehicle crash doubles among drivers with recent marijuana use, and that heavy use of marijuana is associated with impaired memory.


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Other highlights from the report:

• In adults, heavy use of marijuana is associated with impaired memory, persisting a week or more after quitting.

• Maternal use of marijuana during pregnancy is associated with negative effects on exposed offspring, including decreased academic ability, cognitive function and attention.

• Regular marijuana use by adolescents and young adults is strongly associated with developing psychotic symptoms and disorders such as schizophrenia in adulthood.

The Colorado Department of Public Health and Environment review was ordered by state lawmakers. A panel of doctors met for several months to compile the survey, which was delivered to lawmakers last week.

The report also lays out areas where there is limited evidence, or where research is lacking.

For example, the report found insufficient evidence to say how long after smoking pot a person is impaired. Other areas of scanty research:

• Doctors noted there is little available research on the health effects of edible or concentrated marijuana.

• Marijuana smoke contains “many of the same cancer-causing chemicals as tobacco smoke.” But doctors noted there is “limited” or “mixed” evidence to suggest pot-smoking is associated with greater risk of lung cancer or other respiratory health effects.


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The doctors suggested additional education about the health effects of marijuana and asked for increased public-health surveys about how people use pot.

Researchers noted that because marijuana use was illegal nationwide until 1996 — when California voters approved the first medical uses for pot — research is extremely limited. Marijuana research has historically looked for adverse effects, not possible health benefits.

“This legal fact introduces both funding bias and publication bias into the body of literature related to marijuana use,” authors noted.

Colorado last year funded eight studies to examine possible health benefits of marijuana, including treatment for seizures, Parkinson’s disease and post-traumatic stress disorder. Those studies, totaling about $8 million, may not have results for several years.