More than half of our states have legalized marijuana for medical use, and the list of those legalizing recreational marijuana is growing rapidly. Many experts have focused on the positive medical aspects of marijuana to ease certain physical problems, such as chronic pain from nerve damage and painful muscle spasms associated with multiple sclerosis.

However, marijuana contains over 400 chemicals, and their impact on the brain and body is still largely unknown. Although studies have warned of the dangers of smoking pot and its effect on the brain for decades, two recent studies are even more troubling in light of the rush to legalize its recreational use.

"The proponents of legalization tried to make the medicinal benefits the focus and ignored the numerous damaging effects," neurosurgeon Dr. Russell Blaylock told Newsmax Health.

The most recent study, which was published in the Journal of Alzheimer's Disease, found that smoking marijuana lowers blood flow in every area of the brain, including those areas especially vulnerable to Alzheimer's.

Study participants included almost 1,000 marijuana smokers who had psychiatric problems that were resistant to treatment. They underwent a sophisticated imaging study called single photon emission computed tomography (SPECT) that evaluates blood flow and activity patterns.

Compared to healthy non-marijuana users, researchers at Amen Clinics found abnormally low blood flow in almost every area of the brain in virtually every patient who used marijuana. The hippocampus, an area of the brain known to be impacted by Alzheimer's, was especially affected.

"Our research has proven that marijuana users have lower cerebral blood flow than non-users," said researcher Dr. Elisabeth Jorandby. She added that the region of the brain most likely to show differences between marijuana users and non-users because of low blood flow is the hippocampus.

"This work suggests that marijuana use has damaging influences in the brain — particularly regions important in memory and learning and known to be affected by Alzheimer's," Jorandby added.

"Our research demonstrates that marijuana can have significant negative effects on brain function," said Dr. Daniel Amen, founder of Amen Clinics. "The media has given the general impression that marijuana is a safe recreational drug; this research directly challenges that notion. Clearly caution is in order."

"The reduction in cerebral blood flow is quite significant, especially within the hippocampus, where new memories are formed, among other functions," says Blaylock, author of The Blaylock Wellness Report. "Aberrant memories can result, meaning that users will misinterpret their memories and have false memories."

A second recent study, which was conducted in Norway, found that the risk of developing psychosis triples for people who abuse the drug. Several previous studies found that patients with psychotic disorders, such as schizophrenia, were more likely to use marijuana than the general population, but researchers weren't sure if genes or smoking pot caused the disorders.

The Norwegian study examined twins — one of the pair smoked weed and the other didn't — and found that those who smoked were 3.5 times more likely to develop psychosis.

Blaylock questions the march toward legalization of marijuana and fears it will have a great impact in the future: "Chronic pot smoking has been known for years to cause apathy and dysfunctional cognition, among many other health problems."

Studies have linked pot to declines in IQ, impaired ability to think and learn, and an increased risk of dropping out of school.

"With millions smoking this drug on a regular basis — some from a very young age, great concern exists that it will alter their ability to function in society and to hold a job," Blaylock says.

"We are now seeing the result of three generations regularly using a number of illegal drugs — apathy, higher crime rates, poor learning skills, confusion, broken families and an inability to think logically."

Blaylock believes we are already seeing the impact of marijuana in older people. "We are now seeing a much younger age group entering nursing homes for high levels of care, and I think these drugs are playing a significant role," he said.

"Studies have shown that the very young will have access to marijuana, and because the brain undergoes major formation and development until adolescence, this drug can interfere with brain maturation and produce a population that will have difficulty controlling their behavior.

"To legalize this drug will only worsen this situation," Blaylock said.