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HEALTH LESSON: Smoking marijuana

[Yet another tool for teachers.] Some students believe that health lessons are necessarily dull. But try this one. The New York Times reports:

Young adults who started using the drug regularly in their early teens performed significantly worse on cognitive tests assessing brain function than did subjects who were at least 16 when they started smoking, scientists reported on Monday…. [The researchers] surmise that the developing teenage brain may be particularly vulnerable to the ill effects of marijuana….

The study, done in conjunction with brain scans, was small, consisting of 35 chronic marijuana smokers who were 22 years old on average. Twenty had started smoking marijuana regularly before age 16, while 15 started smoking regularly at age 16 or later. All had similar levels of education and income….

Those who had been using marijuana regularly in their early teens smoked more than twice as often as those who started smoking later. The early users also smoked … almost three times as much as the later smokers, … on average, Dr. Gruber said. She nevertheless attributed poor performance on the task to early use of marijuana…

How to Use This Lesson

We recommend that you ask students to read both the full newspaper article (and other articles, too!), and also an authoritative Harvard University press release. Then encourage questions.

Questions for Discussion

Many scientific questions can be raised. Likely, students will have some of their own. Here are a few you can use to begin the classroom discussion:

1. Do the researchers know whether the two groups performed differently before each started smoking?

2. Are people who are already having big problems with life (and cognitive tests) likely to begin smoking at an earlier age than people who are not having such big problems?

3. Why does it not matter that one group of test subjects smoked “more than twice as often” and “almost three times as much”?

4. How do the researchers know — based on this one test given to people later in life (and, apparently, no tests given earlier in life) — that the brains of one group developed in a different way than the brains of the other group?

5. Can you think of even one different explanation that works as well or better?

NOTE: As usual, see  our Teachers’ Guide.

Improbable Research