Prop 64: As THC Levels Hit New Highs, Health Effects Of Marijuana Still A Big Unknown

SACRAMENTO (CBS13) - This week we've explored different aspects of Proposition 64, which would legalize recreational marijuana in California. We went to Colorado to see how they've handled legalization for the last three years, how they regulate and enforce marijuana, and what impacts weed has on business, taxes, and public health.

Colorado consistently leads the nation when it comes to marijuana use.

According to a state report, adults are reporting using marijuana more often than before legalization - 21 percent in 2006 compared to 31 percent in 2014.

Teen use has stayed about the same.

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"We certainly haven't seen anything dramatic in regards to poor health outcomes," said Dr. Larry Wolk.

Wolk is Colorado's Director of Public Health. He says there are notable positives with medical marijuana, but also some documented concerns - especially for young people.

"We certainly know there is negative consequences, certainly for youth with regards to the developing brain," said Wolk.

Wolk says the drug may reduce thinking, memory and learning ability.

There are other notable effects in teens.

"With teenagers, you can see things like a loss of motivation, a loss of drive," he continued.

But is there a widespread public health concern?

"We're unable to see any causation between legalization and an increase in some sort of public health and public safety," said Andrew Freedman, Colorado's Director of Marijuana Coordination.

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According to a federal report, Colorado hospitalizations related to marijuana increased by 3,200 in the years following legalization. The number rose from 8,200 in 2013 to 11,400 in 2014. The increase may be easily explained with inexperienced users.

"The majority of those are occurring among out of state-ers, people who don't live here in Colorado," said Wolk.

An American Medical Association study shows pediatric hospital visits in the state related to marijuana rose from 9 to 47 from 2009 to 2015.

The main cause: kids accidentally eating edibles, which commonly look like cookies or candy.

"We certainly didn't want edible marijuana products to be enticing to kids," said Wolk.

Starting Oct. 1, a new Colorado law will require more identification on edible products.

"It will be a caution sign with an exclamation point with the letters T-H-C," explained Freedman.

Potency is another issue, with products getting stronger.

"Very clear evidence that potency is rising. Average potency has risen substantially," said Rosalie Pacula, a researcher at RAND Drug Policy Research Center.

According to a Colorado State report, and the National Institute of Health, THC - the psychoactive chemical in marijuana - is at an unprecedented level.

Marijuana flowers and buds have risen from a potency of 6 percent in 2003 to an average potency of 17 percent in 2016.

Concentrates, like edibles and oils, average 62 percent in 2016.

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"People are viewing these new products and potencies and intake methods that have never been seen before as safe," said Diane Calrson, with Smart Colorado.

She argues the scientific information to back-up the "safe" claims just aren't there.

The federal government lists weed as an illegal substance, which limits research and leaves it up to special interests groups to make the case of what's safe and what isn't.

"There is a lot of conflicting information out there about the potential effects of marijuana," said Drew Soderborg with California's Legislative Analyst's Office.

He says it's difficult to find credible information for voters in this state. And it's why public health officials in Colorado say they're part of a grand experiment, with the people as the sample.

"I would like to see a more restrictive start so we can understand the science of marijuana and THC a little bit better," said Wolk.

In the next story, we look at the social and societal implications of legal recreation marijuana.