While no psychoactive substance is completely harmless, modern science continues to prove that cannabis is one of the safer and more effective therapeutic agents available. Here’s a look back at some of the most significant marijuana-centric studies published over the past year.

1. Pot Use Doesn’t Adversely Impact IQ

The cumulative use of cannabis by adolescents has no ill effect on intelligence, according to longitudinal data published in January in the Proceedings of the National Academy of Sciences. Investigators evaluated intellectual performance in two longitudinal cohorts of adolescent twins. Participants were assessed for intelligence at ages 9 to 12, prior to any marijuana exposure, and again at ages 17 to 20. They concluded: "In the largest longitudinal examination of marijuana use and IQ change, … we find little evidence to suggest that adolescent marijuana use has a direct effect on intellectual decline.”

2. Cannabis Consumption Is Correlated With Lower BMI

Those who use marijuana, on average, possess a lower body mass index (BMI) than those who abstain from the herb. So reported researchers at the University of Miami this past July in The Journal of Mental Health Policy and Economics. Investigators assessed the relationships between marijuana use and body mass index over time in a nationally representative sampling of American adolescents. They concluded: "[D]aily female marijuana users have a BMI that is approximately 3.1 percent lower than that of non-users, whereas daily male users have a BMI that is approximately 2.7 percent lower than that of non-users." Lower BMI is associated with less risk of heart disease and other potential adverse health issues.

3. Fewer Traffic Fatalities Occur In Medical Cannabis States

The passage of medical marijuana legalization is associated with reduced traffic fatalities among younger drivers, according to data published this month in the American Journal of Public Health. Investigators from Columbia University assessed the relationship between medical cannabis access and motor vehicle accidents over a nearly three-decade period (1985 to 2014). They reported: “[O]n average, MMLs (medical marijuana laws) states had lower traffic fatality rates than non-MML states. …. MMLs are associated with reductions in traffic fatalities, particularly pronounced among those aged 25 to 44 years. … It is possible that this is related to lower alcohol-impaired driving behavior in MML-states.”

4. Pot Patients Spend Less On Prescription Drugs

Patients who reside states where medical cannabis is legal spend less money overall on conventional medications. So determined University of Georgia scientists in July. Researchers assessed the relationship between medical marijuana legalization laws and physicians' prescribing patterns in 17 states over a three-year period (2010 to 2013). Specifically, researchers assessed patients' consumption of and spending on prescription drugs approved under Medicare Part D in nine domains: anxiety, depression, glaucoma, nausea, pain, psychosis, seizures, sleep disorders, and spasticity. Authors reported that prescription drug use fell significantly in seven of the nine domains assessed, and they estimated that nationwide legalization would result in a savings of more than $468 million in annual drug spending.

5. Pot Users No More Likely Than Abstainers to Access Health Care Services

Cannabis consumers are not a drain on the health care system. Researchers at the University of Wisconsin assessed the relationship between marijuana use and health care utilization in a nationally representative sample of US adults aged 18 to 59 years old. Their findings appeared in October in the European Journal of Internal Medicine. They determined that pot users, including habitual consumers, were no more likely than non-users to be admitted to the hospital or to access outpatient health care services. Researchers concluded, "[C]ontrary to popular belief, … marijuana use is not associated with increased healthcare utilization, [and] there [is] also no association between health care utilization and frequency of marijuana use."

6. Marijuana Use History Associated With Better In-Hospital Survival Rates

Patients who test positive for cannabis are less likely to die while hospitalized, according to data published online in November in the journal Cancer Medicine. A team of researchers from the University of Northern Colorado, Colorado State University, and the University of Alabama assessed the relationship between marijuana use and health outcomes among a nationwide sample of 3.9 million hospitalized patients. Researchers reported a correlation between a patient’s history of cannabis use and survival rates, particularly among those admitted for cancer treatment. They concluded, "Odds of in-hospital mortality were significantly reduced among marijuana users compared with non-users in all hospitalized patients as well as cancer patients."

7. More Seniors Are Turning to Cannabis

More seniors are becoming stoners. According to population data published in November in the journal Addiction, marijuana use by those age 50 and older has spiked significantly since 2006. Specifically, authors reported that the prevalence of past-year cannabis has risen approximately 60 percent for those age 50 to 64, and increased 250 percent for those over 65 years of age. It’s understandable why. Older Americans are well aware of the multitude of the severe side effects often associated with conventional medication whereas cannabis is recognized as to possess no risk of fatal overdose and is associated with far fewer significant adverse events.

8. Maternal Marijuana Use Risks Likely Have Been Overstated

The moderate use of cannabis during pregnancy is not an independent risk factor for adverse neonatal outcomes such as low birth weight, according to a literature review published in October in the journal Obstetrics & Gynecology. Investigators at the Washington University School of Medicine in St. Louis reviewed outcomes from more than two-dozen relevant case-control studies published between 1982 and 2015. They reported that the maternal use of tobacco, not marijuana, is likely responsible for adverse events such as pre-term births or children born at a weight below normal for their gestational age. Researchers concluded: "[T]he results of this systematic review and meta-analysis suggest that the increased risk for adverse neonatal outcomes reported in women using marijuana in pregnancy is likely the result of coexisting use of tobacco and other cofounding factors and not attributable to marijuana use itself. Although these data do not imply that marijuana use during pregnancy should be encouraged or condoned, the lack of a significant association with adverse neonatal outcomes suggests that attention should be focused on aiding pregnant women with cessation of substances known to have adverse effects on the pregnancy such as tobacco."

9. Unlike Drinking Booze, Smoking Pot Decreases Aggression

It’s long been presumed that consuming alcohol increases user’s feelings of aggression while cannabis exposure does just the opposite. Data published in July in journal Psychopharmacology confirms it. Investigators from Maastricht University in the Netherlands and Frankfurt University in Germany evaluated subjects' response to aggressive stimuli following exposure to alcohol, cannabis, or placebo. Predictably, researchers reported that alcohol and cannabis intoxication resulted in disparate responses among participants. They concluded, "The results in the present study support the hypothesis that acute alcohol intoxication increases feelings of aggression and that acute cannabis intoxication reduces feelings of aggression following aggression exposure."

10. Fewer Teens Are Abusing Pot In the Era of Legalization

Fewer adolescents are consuming cannabis; among those who do, fewer are engaging in problematic use of the plant, according to data published in July in the Journal of the American Academy of Child & Adolescent Psychiatry. Investigators at Washington University's School of Medicine in St. Louis evaluated government survey data regarding adolescents' drug use habits during the years 2002 to 2013. Researchers reported that the percentage of respondents who said that they had used cannabis over the past year fell by ten percent during the study period. The number of adolescents reporting marijuana-related problems, such as engaging in habitual use of the plant, declined by 24 percent from 2002 to 2013. The study's findings are consistent with previous evaluations reporting decreased marijuana use and abuse by young people over the past decade and a half – a period of time during which numerous states have liberalized their cannabis policies.