Regular marijuana use in adolescence, but not adulthood, may permanently impair brain function and cognition, and may increase the risk of developing serious psychiatric disorders such as schizophrenia, according to a recent study from the University of Maryland School of Medicine. Researchers hope that the study, published in Neuropsychopharmacology will help to shed light on the potential long-term effects of marijuana use, particularly as lawmakers in Maryland and elsewhere contemplate legalizing the drug.
"Over the past 20 years, there has been a major controversy about the long-term effects of marijuana, with some evidence that use in adolescence could be damaging," says the study's senior author Asaf Keller, Ph.D., Professor of Anatomy and Neurobiology at the University of Maryland School of Medicine.
"Adolescence is the critical period during which marijuana use can be damaging," says the study's lead author, Sylvina Mullins Raver, a Ph.D. candidate in the Program in Neuroscience in the Department of Anatomy and Neurobiology at the University of Maryland School of Medicine. "We wanted to identify the biological underpinnings and determine whether there is a real, permanent health risk to marijuana use."
The scientists -- including co-author Sarah Paige Haughwout, a research technician in Dr. Keller's laboratory -- began by examining cortical oscillations in mice. Cortical oscillations are patterns of the activity of neurons in the brain and are believed to underlie the brain's various functions. The scientists exposed young mice to very low doses of the active ingredient in marijuana for 20 days, and then allowed them to return to their siblings and develop normally.
"In the adult mice exposed to marijuana ingredients in adolescence, we found that cortical oscillations were grossly altered, and they exhibited impaired cognitive abilities," says Ms. Raver. "We 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."
The scientists repeated the experiment, this time administering marijuana ingredients to adult mice that had never been exposed to the drug before. Their cortical oscillations and ability to perform cognitive behavioral tasks remained normal, indicating that it was only drug exposure during the critical period of adolescence that impaired cognition through this mechanism.
Dr. Keller's team believes that the results have indications for humans as well. They will continue to study the underlying mechanisms that cause these changes in cortical oscillations.
Source: Science Daily