By M. Gideon Hoyle
Alcohol and marijuana are the two most widely used/abused substances among American teenagers. Frequent consumption of each of these substances is known to significantly alter the normal course of teen brain development.
In a study published in September 2014 in the Journal of Studies on Alcohol and Drugs, researchers from the University of California, San Diego used measurements of brain thickness to track the changes in adolescent brain development found in current teen marijuana and alcohol consumers, as well as in teens who have abstained from the use of these substances for roughly one month.
Teen Alcohol Use
Every year, the National Institute on Drug Abuse and the University of Michigan use a nationwide survey project called Monitoring the Future to track consumption of a range of substances — including alcohol and marijuana — in American teenagers in the 8th, 10th and 12th grades.
In 2013, approximately 39 percent of all U.S. high school seniors drank at least some alcohol in any given month; 26 percent of seniors got drunk in any given month. The overall rate of monthly alcohol consumption in U.S. 10th graders in 2013 was just under 30 percent; almost 13 percent of 10th graders got drunk in the average month. Roughly 10 percent of 8th graders consumed alcohol monthly over the course of the year; 3.5 percent of 8th graders got drunk.
Among all three grades, the rates for monthly alcohol intake and monthly drunkenness fell in comparison to the rates reported for 2012.
Teen Marijuana Use
More than one-fifth (22.7 percent) of all high school seniors were monthly marijuana/cannabis users in 2013, according to the figures compiled through Monitoring the Future; 6.5 percent of teens in 12th grade consumed the drug basically every day. Among 10th graders, the monthly consumption rate for marijuana/cannabis was 18 percent; 4 percent of teens in this grade consumed the drug basically every day. Eighth graders had a 7 percent monthly rate of marijuana/cannabis use in 2013; 1.1 percent of teens in this grade qualified as daily users of the drug.
Monthly rates for marijuana intake rose slightly among 8th and 10th graders in comparison to the figures recorded for 2012, while the monthly rate for 12th graders fell slightly. The rates for daily use were unchanged in comparison to 2012 for 8th and 12th graders; they rose slightly for 10th graders.
Alteration Of Brain Development From Teen Alcohol And Marijuana Use
A wealth of modern studies supports the damaging impact that teen alcohol consumption and teen marijuana consumption can have on critical phases of normal brain development during the gradual transition from adolescence to adulthood.
In the study published in the Journal of Studies on Alcohol and Drugs, the University of California, San Diego researchers used measurements of brain tissue thickness to gauge the impact of alcohol and marijuana consumption on teen brain development and function.
Three groups of teenagers between the ages of 15 and 18 participated in this project: marijuana consumers, marijuana and alcohol consumers, and people with no history of marijuana or alcohol intake. The individuals from all three groups submitted to urine drug tests at the beginning of the study, and then submitted to additional testing 28 days later to verify successful avoidance of substance use.
The researchers used magnetic resonance imaging (MRI) scans and psychological screening procedures to compare tissue thickness and brain function between the groups.
Unusual Thin And Thick Areas Of The Brain
After completing their comparisons, the researchers concluded that teen marijuana use and teen alcohol use are each associated with typical patterns of unusual thickness alteration in specific brain regions.
In some cases, affected areas of the brain become abnormally thin in comparison to the brains of teens who don’t use marijuana or alcohol.
In other cases, affected areas of the brain become abnormally thick. For example, the degree of abnormal thinness in two key brain regions increases along with the amount of marijuana any given teen consumes in his or her lifetime.
Conversely, the degree of abnormal thickness increases throughout the brain along with the amount of alcohol consumed, as well as with the frequency of participation in the drunkenness-inducing practice called binge drinking.
The study’s authors note that the changes in brain thickness they observed were present at the beginning of the project, as well as 28 days into a period of sustained abstinence. They believe that these changes may be a physical manifestation of the brain development damage produced by marijuana and alcohol intake. The thickness alterations may disappear over longer periods of abstinence; however, alterations associated with heavy alcohol or marijuana use may continue to exert their damaging influence well into the future.
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