Marijuana had a big year in 2016: Medical marijuana became legal in half of the 50 states, while other states like California, Massachusetts, and Nevada recently approved the drug's recreational use. Undoubtedly, marijuana has some benefits to human health, such as pain relief, but science tells us to err on the side of caution — marijuana legalization may be moving faster than research would support.

In October, Gallup reported that 60 percent of Americans favored the legalization of marijuana. The drug remains illegal on the federal level and a Schedule I substance, according to the U.S. Drug Enforcement Administration and other agencies. However, states are allowed to regulate how the substance may be used.   

Read: 5 Ways Smoking Pot May Affect You As You Age

This legalization of marijuana comes with both benefits and health risks. Here's some of what we learned this year about risks related to pot use.  

Raises Alzheimer's Risk

Numerous studies have touted marijuana for its protective effects on the brain, from helping brain cells grow to shielding the brain from chronic stress. However, researchers have found long-term marijuana use may may reduce blood flow to the brain, specifically the hippocampus, and increase the susceptibility for Alzheimer's disease. A recent study found pot smokers displayed low blood flow in the hippocampus, which is involved in storing long-term memory, including all past experiences. The hippocampus becomes especially vulnerable to damage at the early stages of Alzheimer’s since the disease leads to dysfunctional neurogenesis (growth of brain cells), which can cause memory impairment.

Worsens Verbal Memory

The long-term use of marijuana is linked to poorer verbal memory at middle age. Researchers in Australia found for each additional five years of marijuana exposure, verbal memory was 0.13 standardized units lower than for those who never used it; this corresponds to the average of one of two participants remembering one word fewer from a list of 15 words for every 5 years of use. The participants' IQ was assessed at age 13 (pre-marijuana use) and again at age 38. Early initiators and persistent users had the largest decline in IQ scores — 8 points compared to those who had never used or those who had used and then stopped.

Weakens Heart Muscles

Marijuana use may increase the chances of developing an often temporary heart condition, stress cardiomyopathy, also known as “broken heart syndrome.” In a study, researchers looked at over 33,000 people hospitalized with stress cardiomyopathy from 2003 to 2011. Among the 210 patients who reported marijuana use before they experienced the symptoms of broken heart syndrome, they found noticeable differences between them and the typical sufferer.

Not only were these patients often younger men instead of older women, but they had fewer known risk factors for the condition, like high blood pressure or Type 2 diabetes. They were also slightly more likely to go into cardiac arrest and require an implanted defibrillator to prevent later cardiac events. These findings suggest marijuana can increase the risk of stress cardiomyopathy.

Read: 3 Most Common Medical Marijuana Strains And Uses

Increases Osteoporosis Risk

Smoking pot is often associated with a case of the munchies, but a recent study in the American Journal of Medicine found smokers are more likely to have lower body weight and broken bones. People who report heavy marijuana use have a large reduction in bone density compared with nonusers. Researchers emphasize there is a real concern that this may put them at increased risk of developing osteoporosis and fractures later in life.

Periodontal Disease

Marijuana use for as long as 20 years has been linked with gum disease, specifically at age 38, according to a study in JAMA Psychiatry. Of the 1,037 participants, 484 reported using tobacco daily at some point in their lives while 675 reported using cannabis in any amount at any point. Researchers asked each participant how often they used cannabis at ages 18, 21, 26, 32, and 38. They also obtained laboratory measures of physical health, including periodontal health, lung function, inflammation, and metabolic health. At ages 26 and 38, the participants themselves also weighed in on how they felt physically.

The findings revealed cannabis could not be linked to physical health problems other than poorer periodontal health at age 38. The researchers suspect cannabis users may be brushing and flossing less than others and more likely to be dependent on alcohol.

Poor Vision

Regular marijuana use can delay how visual information is processed in the eye’s retina. A new study found regular pot smokers experience a slight delay in the functioning of their retinal ganglion cells (RGCs), which work to process incoming visual information and are responsible for connecting the retina to the brain. Moreover, they are able to transform light in the brain through a  series of electrical pulses, called action potentials. However, it’s still unclear whether the delay is permanent or may recede over time when the user stops smoking pot.

Poor Sleep

Marijuana may often be associated with helping users sleep better, but a recent study in the Journal of Addictive Diseases found the drug may be related to a user's sleep troubles. Daily pot smokers actually scored higher on the Insomnia Severity Index and on sleep-disturbance measures than those who used the drug less frequently. For example, 20 percent of the nonsmokers met the criteria for clinical insomnia, compared with 39 percent of the daily users meeting those criteria.

State laws regarding marijuana legalization may be changing, but so is our understanding of the substance's health risks. Future research will investigate whether its benefits outweigh those risks. 

See Also:

What Happens To Your Body After You Stop Smoking Marijuana

The Effects Psychoactive Drugs Have On Physical And Mental Health