Brain

Here are just a few of the health effects you may want to know:

• Marijuana use directly affects the brain—specifically the parts of the brain responsible for memory, learning, and attention.
• The compounds in marijuana can affect the circulatory system and may increase the risk of heart attacks and strokes.
• Smoking marijuana can lead to a greater risk of bronchitis, cough, and phlegm production.
• Marijuana users are significantly more likely than nonusers to develop chronic mental disorders, including schizophrenia. Schizophrenia is a type of mental illness where people might see or hear things that aren't really there (hallucinations).
• Eating foods or drinking beverages that contain marijuana have some different risks than smoking marijuana, including a greater risk of poisoning.
• About 1 in 10 marijuana users will become addicted. For people who begin using before the age of 18, that number rises to 1 in 6.
• Some research shows that using marijuana while you are pregnant[288 KB] can cause health problems in newborns—including low birth weight and developmental problems.
• Marijuana use can slow your reaction time and ability to make decisions when driving[271 KB].

“We see specific morphological changes in the brain to important neurotransmitter systems, and individuals who are exposed to THC early in life show greater sensitivity to opiates than others do,” she said. “We know that the brain definitely adapts to marijuana. It is profoundly changing the receptors and receptor signaling that impact gene expression. And the changes it makes last through adulthood and even into the next generation. So we see that there’s something about the ongoing processes in the developing brain that this drug somehow sensitizes—in the cells, the receptors, and in the signaling cascades—that makes kids more vulnerable to addiction and other problems later.”

“There is a lot of optimism for what components of the marijuana plant may offer on a medicinal level but, like all other drugs, the caveat is that you have to know what it does, what population it can be used for, and who could be vulnerable to its effects. We need a lot more research before we can say anything concrete about its future as a treatment.”

Summary: Cannabis use during pregnancy is associated with abnormal brain structure in children, according to a new study. Compared with unexposed children, those who were prenatally exposed to cannabis had a thicker prefrontal cortex, a region of the brain involved in complex cognition, decision-making, and working memory.

Thus, adolescent THC exposure induced behavioral abnormalities resembling positive and negative schizophrenia-related endophenotypes and a state of neuronal hyperactivity in the mesocorticolimbic dopamine (DA) pathway. Furthermore, we observed profound alterations in several prefrontal cortical molecular pathways consistent with sub-cortical DAergic dysregulation. Our findings demonstrate a profound dissociation in relative risk profiles for adolescent versus adulthood exposure to THC in terms of neuronal, behavioral, and molecular markers resembling neuropsychiatric pathology.  

In 2014, Gilman published research on 18-to-25-year-olds that showed differences in the brain’s reward system between users and nonusers. Teens who smoked marijuana had significant abnormalities in the areas of the brain linked to emotion, motivation, and decision-making (see diagram above). “I got a lot of hate mail after that,” she says.

Participants in a study who had used the drug daily for around three years in their teens had an abnormally shaped hippocampus by the time they were in their early 20s.
They also performed around 18 per cent worse in long-term memory tests than individuals who had never touched the drug.

Medical cannabinoids are here to stay, but intellectual honesty is imperative if we are moving toward exploiting their potential benefits. Owing to rising THC concentrations of products, "medical" marijuana is rarely good medicine. This review has identified the dangers associated with whole­plant marijuana, whether used for recreational or for supposedly medical purposes.

“It’s a natural plant! What’s the big deal?” —A common declaration among youth who believe that the effects of marijuana are harmless and that the substance shouldn’t be regulated.  Regardless of public opinion, the science is clear:  Regular recreational use of marijuana during adolescence is harmful to the brain, which isn’t fully developed until the age of 25.

"Our results suggest that adolescents are particularly vulnerable to develop cognitive impairment from cannabis and that the drug, far from being harmless, as many teens and even adults are coming to believe, can have severe neurotoxic effects on the adolescent brain,"..

Even after controlling for the confounding effect of mental illness symptoms preceding marijuana use, these studies showed an increased risk of developing schizophrenia or mood disorders (depression, anxiety) in adulthood if individuals regularly smoked marijuana during adolescence. The risk was particularly heightened if there was any family history of mental illness (i.e., “genetics provided the loaded gun and marijuana pulled the trigger”). Also, mental illness, among those at risk, tended to show up earlier with marijuana use.