Pot unsafe for teen and young adult brains under construction
Image: A homeless teen with the street name of Blaze, right, smokes marijuana from a glass pipe as Dusty Taylor, 20, fiddles with his lighter at the intersection of 21st Avenue and Stout Street in downtown Denver in July. (Andy Cross, Denver Post file).
Even moderate marijuana use among teens and young people was shown in a study this year to cause abnormalities in the developing brain. Yet as Colorado and other states legalize recreational pot use, the public perception is that it is generally safe.
A nationwide NBC/Wall Street Journal poll in March found that most people thought that alcohol, tobacco and sugar are more harmful to a person’s health than smoking pot. The survey echoedresults finding more teens think it’s safe to use marijuana — although so far, it hasn’t shown up in rising usage in Colorado.
That gap has health professionals worried.
“If there is an increasing perception it’s harmless — cognitively, physically and socially — use is eventually going to track with that,” said Ashley Brooks-Russell, assistant professor with the Colorado School of Public Health at University of Colorado Denver.
“What’s been cemented for me this past year is that we really do need to protect our vulnerable populations, like youth,” said Dr. Larry Wolk, a pediatrician and the director of the Colorado Department of Public Health and Environment.
“On the good-news side, we haven’t yet seen an uptick in youth marijuana use,” Wolk said. “The bad-news side is that more teens are perceiving marijuana as not dangerous or a low risk.”
Years of studies have found diminished memory and cognition in tests of heavy users of pot, or cannabis, with their poorer performances in planning, abstract thinking, understanding rules and impulse control.
Duke University researchers concluded in 2012 that persistent marijuana use begun in the teen years and continued through adulthood can lead to a drop of eight IQ points by a person’s late 30s.
A study released this year took that science a step farther.
A Harvard Medical School and Northwestern University Feinberg School of Medicine study published in the Journal of Neuroscience in April used three types of brain scans on 40 young adults, ages 18-25, who smoked pot moderately, which is up to four times a week on average. Researchers wanted to look at any brain changes.
They found changes in the volume, shape and density of two regions of the brain — those responsible for decision-making, judgment, motivation and emotional behavior — in all the moderate users, even in the seven young adults who smoked one joint a week. But the more they smoked, the greater the abnormalities.
Even moderate use during this critical period of brain development, which extends well beyond the teen years, appears to come with alarming lifelong consequences, researchers concluded.
Adolescents who use marijuana at least 20 days a month are two to four times more likely to develop psychosis than adolescents who do not, according to Dr. Paula Riggs, professor and director of the Division of Substance Dependence in the Department of Psychiatry at the University of Colorado School of Medicine.
It could be that children already at risk for mental illness are more likely to abuse pot. Yet, the brains of people between the ages of 10 and the late 20s are “under construction,” Riggs said, and the psychoactive ingredient in pot, delta-9-tetrahydrocannabinol, or THC, is very disruptive.
Although fewer than 10 percent of adult pot smokers become addicted to pot — compared with 15 percent for alcohol and 32 percent for tobacco — the odds are worse for young users. One of every six adolescents who try it will become a chronic user, Riggs said.
The National Institutes of Health’s 2013 “Monitoring the Future” Survey measures drug use and opinions among U.S. eighth-, 10th- and 12th-graders. The number of high schoolers who think marijuana is dangerous has continued to drop in the past decade. In 2013, about 60 percent of seniors thought pot was harmless.
More than half of all teens already say pot is “sort of or very easy” to get, Brooks-Russell said, and it’s getting progressively easier as youths move through ninth to 12th grades.
Next year, Colorado researchers will look in depth at the question of where adolescents get their pot.