Posted on March 1, 2010

Marijuana is abused more frequently than any other street drug in the U.S. It comes from the cannabis plant, and is typically smoked. THC (which stands for delta-9-tetrahydrocannabinol) is the primary chemical in marijuana which affects the brain.

When you smoke marijuana, the THC quickly goes into the bloodstream from your lungs. Your blood transfers it to the organs in your body, including your brain. THC targets certain sites in your brain known as cannabinoid receptors. The resulting activity in the brain causes a pleasurable “high”. Most people who smoke marijuana experience feelings of relaxation and loosening of inhibitions. They also often lose track of time.

Unfortunately, marijuana use can also cause paranoia, coordination problems, impaired problem solving, memory problems, decreased motivation, poor judgment, anxiety and hallucinations.

Scientists have long been concerned about the effects of marijuana on the brains of adolescent users. It appears their concern is warranted. Recent research conducted by Dr. Gabriella Gobbi of McGill University Health Center suggests that when adolescents use cannabis daily, the consequences may include anxiety, depression, and permanent effects on their brains.

The purpose of her research was to determine if adolescents were more vulnerable to the neurological impact of cannabis use than adults. She also wanted to study the effects of cannabis on young users. The research of Dr. Gobbi suggests that cannabis affects serotonin and norepinephrine, two neurotransmitters associated with both anxiety and mood disorders.

Adolescents who are exposed to this drug are thus more vulnerable to stress long-term, and may be more susceptible to developing a mood disorder.

While previous research has focused primarily on the effects of marijuana use on adolescent behavior, Dr. Gobbi’s study focused on the neurobiological relationship between adolescent cannabis use and anxiety and depression. Her research is the first to show that use of marijuana is especially damaging for teens – more so than for adults. In other words, the long-term effects of the drug when used during adolescent years may be irreversible.

Dr. Gobbi’s study was recently published in Neurobiology of Disease.