Heavy marijuana use during adolescence has now been linked to lower IQ scores later in life, according to a study published last month by the National Academy of Sciences.

The study, which tracked 1,037 subjects from birth to age 38 years, found that those who began smoking marijuana as teenagers and used it regularly throughout adulthood scored approximately 8 points lower on an IQ test than they had at age 13 years. In comparison, the IQ scores of non-users, as well as those who started using marijuana as adults, were stable. Small to medium declines in memory, processing speed, and executive function were also seen in regular users.

“We know that there are developmental changes occurring in the teen years and up through the early 20s, and the brain may be especially vulnerable during this time,” said Dr. Madeline Meier, a researcher at Duke University and lead author of the study, in an August 27 New York Times article.

The results of this study are in direct contrast with beliefs common among adolescents that marijuana use is harmless to health. “Adolescents are initiating cannabis use at younger ages, and more adolescents are using cannabis on a daily basis,” study authors said. “Findings are suggestive of a neurotoxic effect of cannabis on the adolescent brain and highlight the importance of prevention and policy efforts targeting adolescents.”

Although the authors ruled out several alternative explanations for the neuropsychological effects (such as hard drug use, alcohol dependence, and schizophrenia), they acknowledge that their results must be interpreted within the context of the study’s limitations. “There may be some ‘third’ variable that could account for the findings,” they said. “The data cannot reveal the mechanism underlying the associations between persistent cannabis dependence and neuropsychological decline.”

What do you think? Is there a disconnect between common beliefs about marijuana use and the reality of its long-term effects on health? PAR wants to hear from you, so leave a comment and join the conversation!

Meetings are a regular part of working life, an opportunity to collaborate, solve a problem, or accomplish a goal. Many of us assume that meetings, while sometimes tedious or dull, are still the best way to bring good ideas to the table. New research led by scientists at the Virginia Tech Carilion Research Institute, however, suggests quite the opposite—meetings may, in fact, make us dumber.

The study’s authors assert that the social dynamic that occurs in meetings can have a detrimental effect on our ability to think clearly. “You may joke about how committee meetings make you feel brain dead, but our findings suggest that they may make you act brain dead as well,” said co-author Read Montague, in a recent interview with msnbc.com author Linda Carroll.

In the study, researchers used functional magnetic resonance imaging (fMRI) to look at the brains of college-student volunteers as they took an IQ test. Next, the students were divided into groups with similar IQs and given a second test. Each time they answered a question during the second round of testing, they were given feedback about their performance compared to others in the group. Although the volunteers were well matched in terms of initial IQ scores, scores dropped dramatically when students were receiving constant feedback about their performance relative to others in their group.

According to lead author Kenneth Kishida, constant reminders of status were stimulating parts of the brain involving fear, anxiety, and emotional response—and this was causing the students to perform poorly on the test. In the context of a meeting, such negative feelings can be triggered by a sense that others in the group are smarter or better prepared—even when they aren’t. According to Kishida, the perception alone can stifle our best thinking.

What do you think? Do meetings help or hinder intelligence and creativity? Leave a comment and join the conversation!

PAR is proud to announce that the following software products are now available for direct download to your computer through our Web site, www.parinc.com:

• Reynolds Intellectual Assessment Scales™ Interpretive Report (RIAS™-IR)


• Wide Range Achievement Test 4 Interpretive Report (WRAT4-IR)


• Wide Range Achievement Test 4 Scoring Program (WRAT4-SP)


• Behavior Rating Inventory of Executive Function® Software Portfolio (BRIEF®-SP)


• Behavior Rating Inventory of Executive Function®–Adult Version Software Portfolio (BRIEF®-A SP)


• Personality Assessment Inventory™ Software Portfolio (PAI®-SP) Counter Serial Numbers


• Personality Assessment Inventory™–Adolescent Software Portfolio (PAI®-A SP) Counter Serial Numbers

Simply click on the product page link and select the Download item code or the Download with CD-ROM item code to have a backup CD mailed to you.

We hope you will enjoy being able to download software products directly from PAR and hope to make more products available in this way in the future. We are conducting a survey to see which other software products you would like to be made available in this format.


We appreciate your feedback. Thank you for helping us to understand how we can better serve you.