The Teen Brain on Drugs and Alcohol: A Dangerous Combination
New research shows the negative impact of alcohol and marijuana use on developing brains that can last into adulthood.
-- by Suzanne Boothby
Chronic alcohol and marijuana use in adolescence creates worsened neurocognitive abilities into later adolescence and adulthood, according to a new study published in a special online issue of Alcoholism: Clinical & Experimental Research.
Substance abuse during youth is associated with poorer neural structure, function, and metabolism, as well as worsened neurocognitive abilities into later adolescence and adulthood. Scientists believe this connection is due to biological and psychosocial transitions that occur during adolescence increasing teenagers' vulnerability to neurotoxic influences.
The current study looked at longitudinal changes in fiber tract integrity, and it supports previous findings of reduced white-matter integrity in adolescents who abuse drugs and alcohol. "White matter" refers to areas of the brain composed of connecting axons, which appear white in color.
"Prior research has not clearly demonstrated that this white matter disorganization is caused by alcohol or marijuana use,” says Duncan Clark, Associate Professor of Psychiatry at the University of Pittsburgh Medical Center. “In some studies where adolescents are studied only once, white matter disorganization may have been present prior to alcohol or marijuana use."
Marijuana is the most common illicit drug in the United States, according to the National Survey on Drug Use and Health. The American Academy of Child and Adolescent Psychiatry estimates that average age of first marijuana use is 14, and alcohol use can start before age 12. About 20 million adults in the United States abuse alcohol and more than half of these alcoholics started drinking heavily when they were teenagers.
The Expert Take
Research has shown differences in the brains of teens who use alcohol and marijuana as compared to teens who do not use these drugs or report only minimal use.
"Alcohol and marijuana may have a negative impact by altering important cellular communication in the brain, preventing development of new healthy cells, and/or causing inflammation, which can adversely impact healthy brain development in many ways,” says study author Joanna Jacobus, postdoctoral fellow at the University of California, San Diego. “For example, the results can lead to changes in brain structure, such as volume, and function, such as activity."
One of the biggest threats to teenagers experimenting with alcohol and drugs is the habits they can form, which could last into adulthood.
"Maturation of the brain during adolescence is thought to be the foundation for self-control," Clark said. "The developing adolescent brain, compared to the fully developed adult brain, is also probably more vulnerable to alcohol neurotoxicity. Adolescents are vulnerable to loss of control and, when this loss of control involves substance use, excessive or risky substance use can have adverse consequences."
Dr. Stefan Kertesz, an associate professor at University of Alabama at Birmingham has studied the health impacts of marijuana and has found when adults use it moderately there is little risk. Still, he encourages people to look at the big picture.
“Marijuana is still an illegal drug, and it has many complicated effects on the human body and its function,” said Kertesz in a press release. “In our findings we see hints of harm in pulmonary function with heavy use, and other studies have shown that marijuana use increases a user’s likelihood of a heart attack, according to the American Heart Association, and impairs the immune system's ability to fight disease, according to the National Institute on Drug Abuse.”
Source and Method
Researchers followed 92 adolescents (63 males, 29 females), aged 16 to 20 years, for 18 months. They divided the subjects into two groups: 41 with extensive alcohol and marijuana use histories by mid-adolescence, and 51 with consistently minimal, if any, substance use.
Participants were part of an ongoing longitudinal study of substance use in adolescence with teens recruited from local schools from 2005 to 2007. Both groups received diffusion tensor imaging and detailed substance use assessments, along with toxicology screening, at baseline and 18-month follow-ups, as well as interim substance-use interviews every six months.
"Our findings underscore that early initiation of alcohol and marijuana use can have negative implications on the brain," says Jacobus. "We hope this information can be communicated to teens to help them understand why drinking during adolescence is discouraged. In the future, biomarkers such as tissue health may help identify teens that are particularly vulnerable for engaging in riskier behaviors such as drinking."
While laws are becoming friendlier to marijuana use, current research shows teens should use caution when it comes to chronic use. Since 1996, 18 states and Washington, D.C. have legalized the medical use of marijuana to help manage the symptoms of many diseases, including cancer and AIDS. Colorado and Washington State both voted in November to legalize the recreational use of marijuana.
Jacobus also published 2009 research examining the influence of substance abuse on adolescent brain development. The study suggested that substance use in adolescence led to abnormalities in brain functioning.
While chronic marijuana use might have an impact on the brain, some research has found that moderate amounts do not affect the lungs as some might expect. A 2011 JAMA study found that occasional and low cumulative marijuana use was not related to adverse effects on pulmonary function. Since marijuana may have beneficial effects when it comes to pain control, appetite, mood or management of other chronic symptoms, the authors confirmed that occasional use for these purposes would not create adverse consequences.