New research offers another compelling reason to keep teens away from pot.

A team from the Schulich School of Medicine & Dentistry at Western University in Canada discovered the schizophrenia-like effects on adolescent brains of delta-9-tetrahydrocannabinol or THC, the psychoactive ingredient of marijuana.

They published their findings Jan. 4 in the journal Cerebral Cortex.

Schizophrenia Signs In Young Rats

The study exposed adolescent and adult rats to THC and tested their behaviors, particularly those typically observed in schizophrenia and other conditions. These include social interaction, cognition, anxiety levels, and motivation.

What they found: young rats exhibited substantial and persistent behavioral, neuronal, and molecular changes identical to those found in schizophrenia and other neuropsychiatric disorders. They were withdrawn from others, exhibited greater anxiety, and had abnormal dopamine levels – conditions that continued into early adult phase.

Adult rats exposed to THC, on the other hand, did not show the same changes. While they also experienced social cognition and memory problems after THC exposure, the adult rodents did not undergo harmful long-term effects.

Study author and psychiatry professor Dr. Steven Laviolette highlighted their study’s importance in light of teens’ common marijuana use and the government’s move toward legalizing the common substance.

Dr. Laviolette emphasized adolescence as a critical time for brain development.

“Health policy makers need to ensure that marijuana, especially marijuana strains with high THC levels, stays out of the hands of teenagers,” he said, adding that marijuana use among adults showed no serious risk.

Lead author Dr. Justine Renard cited not just a rise in adolescent use of cannabis, but also increasing THC content in newer cannabis strains.

“[This] improves our knowledge of how adolescent exposure to THC may lead to the onset of schizophrenia in adulthood,” Dr. Renard said.

Cannabis Use In The U.S.

In the United States, marijuana remains the most commonly used illegal drug, comprising 81 percent of illicit drug users based on the 2013 National Survey on Drug Use and Health.

Marijuana use is particularly prevalent among teens and young adults, where most measures of cannabis use by 8th, 10th, and 12 graders kept steady in the last few years while perception of risks steadily declined.

In 2014, 11.7 percent among 8th graders reported using marijuana in the past year and 6.5 percent disclosed current use. In 10th graders surveyed, 27.3 percent used pot in the last year while 16.6 percent admitted to current use.

Attitudes and legislation around marijuana use are also shifting, with 23 states now allowing use of the substance for medicinal purposes. Four states allow recreational use.

"Given changing laws and attitudes toward marijuana, a balanced presentation of the likelihood of adverse consequences of marijuana use to policy makers, professionals and the public is needed," urged a study last October in the journal JAMA Psychiatry.

The study noted an increase in marijuana dependence among Americans from 2012 to 2013 compared to 10 years before. The spike was not really caused by medical reasons, as reflected by the researchers’ in-person interviews with over 36,000 Americans over age 18.

Recently, New York joined the roster of states with comprehensive programs for medical marijuana use, as heralded by the opening of its first eight dispensaries that will provide different tinctures, vapors, and concentrates made from the drug.

Photo: James St. John | Flickr

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