Yet Another Study Finds That Cannabis Use Is Not Independently Linked With IQ Decline

Marijuana researchCannabis use by teens is not independently linked with adverse changes in intelligence quotient or executive functioning, according to longitudinal data published online ahead of print in the journal Addiction.

A team of investigators from the United States and the United Kingdom evaluated whether marijuana use is directly associated with changes over time in neuropsychological performance in a nationally representative cohort of adolescent twins. Authors reported that “family background factors,” but not the use of cannabis negatively impacted adolescents’ cognitive performance.

They wrote: “[W]e found that youth who used cannabis … had lower IQ at age 18, but there was little evidence that cannabis use was associated with IQ decline from age 12 to 18. Moreover, although cannabis use was associated with lower IQ and poorer executive functions at age 18, these associations were generally not apparent within pairs of twins from the same family, suggesting that family background factors explain why adolescents who use cannabis perform worse on IQ and executive function tests.”

Investigators concluded, “Short-term cannabis use in adolescence does not appear to cause IQ decline or impair executive functions, even when cannabis use reaches the level of dependence.”

Their findings are consistent with those of several other studies – including those here, here, here, and here – finding that cannabis use alone during adolescence does not appear to have a significant, direct adverse effect on intelligence quotient.

widely publicized and still often cited New Zealand study published in 2012 in The Proceedings of the National Academy of Sciences reported that the persistent use of cannabis from adolescence to adulthood was associated with slightly lower IQ by age 38. However, a follow up review of the data published later in the same journal suggested that the observed changes were likely due to socioeconomic differences, not the subjects’ use of cannabis. A later study by the initial paper’s lead investigator further reported that the effects of persistent adolescent cannabis use on academic performance are “non-significant after controlling for persistent alcohol and tobacco use.”

Pattern of marijuana use during adolescence may impact psychosocial outcomes in adulthood

A pattern of escalating marijuana use in adolescents is linked to higher rates of depression and lower educational accomplishments in adulthood.

Study: No Increase In Problematic Cannabis Use By Young People Following Changes In Marijuana’s Legal Status

no_marijuanaYet another study has once again affirmed that the regulation of marijuana for medical or recreational purposes is not associated with increases in problematic cannabis use by young people.

Writing in the Journal of Clinical Psychiatry, federal investigators from the US National Institute on Drug Abuse and the Substance Abuse Mental Health Services Administration evaluated marijuana use rates among young people (ages 12 to 17) between the years 2002 and 2014.

Researchers reported that the prevalence of past-year cannabis use by youth fell 17 percent during this time period. The prevalence of problematic use by young people fell by 25 percent – with a downward trend starting in 2011.

“In the United States, compared to 2002, even after adjusting for covariates, cannabis use decreased among youth during 2005-2014, and cannabis use disorder declined among youth cannabis users during 2013-2014,” authors concluded.

The study’s findings are consistent with those of numerous other papers reporting no uptick in youth marijuana use or abuse following the enactment of marijuana regulation, including those here, here, here, here, here, here, and here.

An abstract of the study, “Cannabis use and cannabis use disorders in the United States, 2002-2014,” appears online here.

Study: Alcohol Use, But Not Cannabis, Associated With Changes In Brain Structure

marijuana_seedlingAlcohol consumption is associated with negative changes in gray matter volume and in white matter integrity, while cannabis use is not, according to data published online ahead of print in the journal Addiction.

Investigators from the University of Colorado, Boulder and the Oregon Health & Science University evaluated neuroimaging data among adults (ages 18 to 55) and adolescents (ages 14 to 18). Authors identified an association between alcohol use and negative changes in brain structure, but identified no such association with cannabis.

“Alcohol use severity is associated with widespread lower gray matter volume and white matter integrity in adults, and with lower gray matter volume in adolescents,” they concluded. By contrast, “No associations were observed between structural measures and past 30-day cannabis use in adults or adolescents.”

Researchers acknowledged that their findings were similar to those of prior studies “suggesting that regionally specific differences between cannabis users and non-users are often inconsistent across studies and that some of the observed associations may actually be related to comorbid alcohol use.”

A 2015 brain imaging study published in The Journal of Neuroscience similarly reported that cannabis use was not positively associated with adverse changes in the brain, but that alcohol “has been unequivocally associated with deleterious effects on brain morphology and cognition in both adults and adolescents.”

Longitudinal data published in June in the British Medical Journal reported, “Alcohol consumption, even at moderate levels, is associated with adverse brain outcomes including hippocampal atrophy.”

An abstract of the study, “Structural Neuroimaging Correlates of Alcohol and Cannabis Use in Adolescents and Adults,” appears online here.

Legal cannabis laws impact teen use

A new study has found that adolescents living in medical marijuana states with a plethora of dispensaries are more likely to have tried new methods of cannabis use, such as edibles and vaping, at a younger age than those living in states with fewer dispensaries.

Rates of marijuana use, heavy use, and cannabis use disorder depend on where you live

Adult marijuana use rose significantly in states that passed loosely regulated medical marijuana laws (MMLs) according to a new study. The highest increases were reported among adults ages 26 and over. Little change was found in past-month marijuana use among adolescents or young adults between the ages 18 and 25.

Study: No Increase In Problematic Cannabis Use Following Passage Of Medical Marijuana Laws

no_marijuanaThe enactment of medical marijuana laws is not associated with increased rates of problematic cannabis use, according to data published online in the journal Addiction.

Columbia University investigators assessed cannabis use trends in states in the years following the passage of medicalization. They reported “no significant change in the prevalence of past-month marijuana use among adolescents or young adults (those ages 18 to 25)” following legalization. They also found no evidence of increased cannabis abuse or dependence by either young people or adults. States with largely unregulated medical programs were associated with increased self-reported use by adults age 26 and older, but states with stricter programs were not.

The study’s findings are consistent with those of numerous other papers reporting no uptick in youth marijuana use or abuse following medical marijuana regulation, including those here, here, here, here, here, and here. The findings contradict those of a recent, widely publicized paper in JAMA Psychiatry which speculated that medical marijuana laws may increase the prevalence of cannabis use disorder among adults.

An abstract of the study, “Loose regulation of medical marijuana programs associated with higher rates of adult marijuana use but not cannabis use disorder,” is online here.

Delaying marijuana smoking to age 17 cuts risks to teens’ brains, new study suggests

Adolescents who smoke marijuana as early as 14 do worse by 20 points on some cognitive tests and drop out of school at a higher rate than non-smokers. But if they hold off until age 17, they’re less at risk.

Marijuana Use Continues Rapid Decline Among Younger Teens

no_marijuanaSelf-reported marijuana use continues to fall among younger teens, according to federally commissioned, nationwide survey data compiled by the University of Michigan.

Results from the 2016 edition of the Monitoring the Future survey find that marijuana use by 8th-graders and 10th-graders is declining year by year. Further, a greater percentage of younger teens now say that their ability to obtain marijuana is more difficult than ever before.

Marijuana use patterns among 12th-graders have held steady since 2011, the survey reported.

Approximately 50,000 students are surveyed annually as part of the University of Michigan study.

Since the mid-1990s, self-reported lifetime use of cannabis has fallen 44 percent among 8th-graders, 30 percent among 10th-graders, and ten percent among 12th-graders. Twenty-nine states have legalized the medical use of cannabis, and eight of those states have also regulated the adult use of marijuana, since that time.

Overall, teens’ self-reported use of alcohol and/or any illicit substance aside from marijuana is at a historic low.

Previous federally funded surveys by the US Centers for Disease Control and others have similarly reported that changes in statewide marijuana laws are not associated with rising levels of youth use.

N-acetylcysteine shows early promise in reducing alcohol use in marijuana-dependent teens

N-acetylcysteine (NAC) reduced alcohol use in a small cohort of marijuana-dependent adolescents who exhibited reductions in marijuana use, report researchers. In this secondary analysis of data from an earlier trial of NAC in marijuana-dependent adolescents, researchers show that reduced marijuana use was associated with reductions in alcohol consumption in the NAC-treated, but not placebo-treated teens.

Study: Marijuana Retailers Not Selling To Youth

mj_salesAge restrictions in legal marijuana states are effectively keeping cannabis out of the hands of minors, according to newly published data in the Journal of Studies of Alcohol and Drugs.

A team of investigators from California, Colorado, and New Mexico assessed whether licensed retail cannabis facilities would sell to pseudo-underage buyers who failed to show proof of age.

Authors reported, “Compliance with laws restricting marijuana sales to individuals age 21 years or older with a valid ID was extremely high and possibly higher than compliance with restrictions on alcohol sales.”

They concluded, “The retail market at present may not be a direct source of marijuana for underage individuals.”

Similar assessments of facilities in other jurisdictions have also shown that the overwhelming majority of marijuana retailers refuse sales to apparent minors.

A pair of studies published earlier this week from Columbia University researchers reported that changes in marijuana’s legal status are “not associated with higher prevalence rates of marijuana use among adolescents.”

An abstract of the study, “Pseudo-Underage Assessment of Compliance With Identification Regulations at Retail Marijuana Outlets in Colorado,” appears here.

Studies: Changes In Marijuana’s Legal Status Not Associated With Increased Use By Young People

no_marijuanaChanges in marijuana’s legal status under state law is not associated with increased cannabis use or with its perceived availability by young people, according to pair of recently published studies.

In the first study, published online in the journal Substance Use & Misuse, researchers at Columbia University in New York surveyed the marijuana use habits of a national sampling of 1,310 adolescents between the years 2013 and 2015. Investigators assessed whether respondents from states with liberalized cannabis policies were more likely to acknowledge having consumed cannabis compared to those residing in jurisdictions where the substance remains criminally prohibited.

Authors reported that the study’s findings “failed to show a relationship between adolescentsuse of marijuana and state laws regarding marijuana use.” … [They] suggest that eased sanctions on adult marijuana use are not associated with higher prevalence rates of marijuana use among adolescents.”

In the second study, published in the journal Drug and Alcohol Dependence, a team of investigators from Columbia University, the University of California at Davis, and Boston University examined the relationship between medical cannabis laws and the prevalence of marijuana availability and use by both adolescents and by those age 26 or older. Authors reported no changes over a nine-year period (2004 to 2013) with regard to the past-month prevalence of marijuana use by those ages 12 to 17 or by those between the ages of 18 and 25. Those age 25 and younger also experienced no change in their perception of marijuana’s availability. By contrast, self-reported marijuana use and availability increased among adults age 26 or older over this same time period.

The conclusions are similar to those of numerous separate studies reporting that changes in marijuana’s legal status are not associated with any uptick in teens’ use of the substance, such as those here, here, here, and here.

Abstracts of the two studies, “Is the Legalization of Marijuana Associated With Its Use by Adolescents?” and “State-level medical marijuana laws, marijuana use and perceived availability of marijuana among the general U.S. population,” appear online here and here.

CDC: Young People Say Marijuana Is Becoming Less Available

no_marijuanaProhibitionists often claim that legalizing and regulating marijuana will increase youth access to the plant. But newly released federal data says just the opposite.

Fewer young people are reporting that marijuana is ‘easy’ to obtain, according to an analysis released this week by the US Centers for Disease Control.

Investigators from the Substance Abuse and Mental Health Services Administration and the CDC evaluated annual data compiled by the National Survey on Drug Use and Health for the years 2002 to 2014. Researchers reported that the percentage of respondents aged 12 to 17 years who perceived marijuana to be “fairly easy or very easy to obtain” fell by 13 percent during this time period. Among those ages 18 to 25, marijuana’s perceived availability decreased by three percent.

Researchers further reported that “since 2002, the prevalence of marijuana use and initiation among U.S. youth has declined” – a finding that is consistent with numerous prior studies.

By contrast, authors reported an uptick in use among adults. However, they acknowledged that this increase in adult marijuana consumption has not been associated with a parallel increase in problematic use. There has been “steady decreases in the prevalence of marijuana dependence and abuse among adult marijuana users since 2002,” the study found. Those adults experiencing the greatest percentage increase in marijuana use during the study period were respondents over the age of 55.

A separate analysis of the data published in the journal Lancet Psychiatry similarly acknowledged no observed increase in marijuana use disorders. A previous assessment of marijuana use patterns since 2002, published earlier this year in JAMA Psychiatry, also reported a decline in the percentage of adults reporting problems related to their marijuana use.

Full text of the CDC study, “National estimates of marijuana use and related indicators – National Survey on Drug Use and Health, 2002-2014,” appears online here.

Adolescent alcohol, marijuana use leads to poor academic performance, health problems

Adolescents who use both marijuana and alcohol during middle school and high school are more likely to have poor academic performance and mental health during high school, according to a new study that followed a group of students over a seven-year period. However, the study found marijuana use was predictive of poorer functioning across more areas, including lower academic functioning, being less prepared for school, more delinquent behavior and poorer mental health.

Trauma in childhood linked to drug use in adolescence

Latest research from a national sample of almost 10,000 US adolescents found psychological trauma, especially abuse and domestic violence before age 11, can increase the likelihood of experimentation with drugs in adolescence, independent of a history of mental illness. This is the first study to document these associations in an American national sample of adolescents.

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