Scientists have identified a mechanism in the brain that seems to explain how long-term marijuana use in the teenage years might lead to schizophrenia and other similar psychiatric diseases in adulthood. They also showed how drugs might be able to reverse the schizophrenia-like symptoms. Share on Pinterest Canadian researchers have found that they might be able to reverse the schizophrenia-like symptoms associated with prolonged teenage marijuana use. In a paper published in the journal Scientific Reports, researchers from the University of Western Ontario in Canada report how they showed this effect in laboratory rats. Marijuana refers to the dried parts – that is, the flowers, leaves, stems, and seeds – of the Cannabis sativa or Cannabis indica plants. The plants contain a number of psychoactive (mind-altering) compounds, or cannabinoids, with the main one being delta-9-tetrahydrocannabinol (THC). In the United States, marijuana is the “most commonly used illicit drug,” and use is widespread among adolescents and young adults. Last year, around 9.4 percent of 8th graders and 23.9 percent of 10th graders in the U.S. said that they had used marijuana at least once in the previous year. However, the highest use was among 12th graders, with 35.6 percent of them saying that they had used it at least once in the previous year, and 6 percent saying that they used it every day or nearly every day.

Focus on GABA In their study paper, senior author Steven Laviolette – a professor at the University of Western Ontario’s Schulich School of Medicine and Dentistry – and colleagues explain that while it is “still a matter of debate,” some studies have suggested that long-term exposure to THC raises the long-term risk of schizophrenia and other psychiatric diseases. In fact, in some of their own previous work with animal models, the team had found that long-term exposure to THC leads to “persistent abnormalities in adulthood resembling schizophrenia.” They had also found that these abnormalities are accompanied by changes in the prefrontal cortex region of the brain and increased activity in the region’s dopamine system. Dopamine is a chemical messenger, or neurotransmitter, that plays a number of roles – such as helping to regulate brain centers involved with reward, pleasure, movement, and emotion. Insufficient dopamine is a hallmark of Parkinson’s disease. However, the researchers note that the underlying mechanism linking the brain changes to the schizophrenia-like symptoms has remained somewhat of a mystery, and so they devised the new study to investigate it further, focusing on another chemical messenger called GABA. “GABA is an inhibitory neurotransmitter and plays a crucial role in regulating the excitatory activity in the frontal cortex, so if you have less GABA, your neuronal systems become hyperactive leading to behavioural changes consistent with schizophrenia,” explains study co-author Justine Renard, a postdoctoral fellow.