Drugs

Marijuana Use During Adolescence, Not Adulthood, May Cause Permanent Mental Illness

Marijuana Use During Adolescence, Not Adulthood, May Cause Permanent Mental Illness
Mice exposed to THC as adolescents showed disrupted neural patterns as adults, whereas adult mice exposed to THC showed no disruption. Creative Commons

Marijuana has been welcomed across the nation in recent years. However, while there have been studies upon studies asserting its health benefits, there hasn't been nearly as much effort put into its effects on children's brains, and for obvious reasons — nobody is going to give kids marijuana for experimental purposes. But a team of researchers wanted to see what the possible effects of marijuana could be on a young mind, so they used mice, and found that marijuana could permanently impair brain function and cognition, and may even increase the risk of mental disorders.

"Previous research has shown that children who started using marijuana before the age of 16 are at a greater risk of permanent cognitive deficits, and have a significantly higher incidence of psychiatric disorders such as schizophrenia," Dr. Asaf Keller, professor of anatomy and neurobiology at the University of Maryland, School of Medicine, said in a statement. "There likely is a genetic susceptibility, and then you add marijuana during adolescence and it becomes the trigger."

Schizophrenia is a chronic, severe brain disorder which can cause a person, among other symptoms, to hear voices or believe others are reading their minds, controlling their thoughts, or plotting harm. It appears in about one percent of the U.S. population, however, 10 percent of people who have a first-degree relative with the disorder are likely to have it as well, according to the National Institutes of Health.

THC's Effect On Neural Patterns

The research team wanted to see if marijuana use during adolescence, a time when a kid's whole body is developing, could be dangerous, and if so, they wanted to "identify the biological underpinnings."

They began their experiments by administering low doses of the active ingredient in marijuana, tetrahydrocannabinol (THC), to young mice for 20 days, after which they were returned to their siblings and allowed to develop normally.

The researchers were interested in seeing how THC affected cortical oscillations in the mice. Cortical oscillations are defined patterns of activity by the brain's neurons that are believed to play a part in the brain's functions. However, while they are well-defined for people of normal health, those who have schizophrenia and other psychiatric disorders tend to have abnormal oscillations.

The researchers found that the mice that were exposed to marijuana while young grew up to have oscillations that were "grossly altered." They also found "impaired cognitive behavioral performance in those mice."

"The striking finding is that, even though the mice were exposed to very low drug doses, and only for a brief period during adolescence, their brain abnormalities persisted into adulthood," lead author of the study Dr. Sylvina Raver said.

The researchers repeated the experiment to see if these effects only happened in adolescent mice. They gave THC to adult mice that hadn't previously been exposed to it, and found that the cortical oscillations in these mice stayed the same.

But why did THC only affect the brains of young mice?

"We looked at the different regions of the brain," Dr. Keller said. "The back of the brain develops first, and the frontal parts of the brain develop during adolescence. We found that the frontal cortex is much more affected by the drugs during adolescence. This area of the brain controls executive functions such as planning and impulse control. It is also the area most affected in schizophrenia."

Researchers believe these results could have implications for humans as well and plan on delving deeper into marijuana's effects on cortical oscillations.

"We are hoping we will learn more about schizophrenia and other psychiatric disorders, which are complicated conditions," Dr. Keller said. "These cognitive symptoms are not affected by medication, but they might be affected by controlling these cortical oscillations."

Marijuana's Effects On Human Children and Teens

In humans, marijuana use among teens who participated in a study showed that they were 3.5 times more likely to attempt suicide if they started consuming marijuana at 17 years old or younger. These teens were also more likely to develop symptoms of depression.

The detriments of marijuana use among children could also be seen in Colorado, where legalization of marijuana brought about an increased number of emergency room visits due to marijuana exposure, according to a study published in JAMA Pediatrics.

Specifically, 14 kids, ages 12 and younger, experienced illnesses, including lethargy, ataxia, and respiratory insufficiency. Two of these cases were also treated in an intensive care unit.

"The finding reignites the debate over whether and how legalized marijuana impacts children and adolescents," wrote pediatrician Sharon Levy. She added that marijuana use among adolescents is on the rise, since so much of the country asserts its harmlessness.

 

Source: Raver S, Keller A, Haughwout S. Adolescent Cannabinoid Exposure Permanently Suppresses Cortical Oscillations in Adult Mice. Neuropsychopharmacology. 2013.

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