Premise: Zhang and his co-workers performed behavioral tests on two purified cannabinoids. The test results indicated that these two cannabinoids have anti-anxiety and antidepression-like effects in rats that may depend on the ability of cannabinoids to promote the production of new neurons in the hippocampus. Marijuana contains a complex mixture of chemicals including cannabinoids and may have somewhat different behavioral effects than the purified cannabinoids tested so far.
Hypothesis: Zhang and his coworkers did not perform any behavioral tests.