Adolescent cannabis or THC exposure in rats did not produce lasting anxiety, depression, or cognitive effects in adulthood

Despite testing both cannabis smoke and THC at multiple doses during the adolescent period (P29-49 or P35-45), adult rats showed no significant effects on anxiety (open field, elevated plus maze), depression (sucrose preference, forced swim), or cognition (novel object recognition) after abstinence until P70. Some subtle sex differences were slightly attenuated.

Two experiments in Long-Evans rats. Cannabis smoke exposure PD 29-49 or ascending THC doses PD 35-45. Adult behavioral testing at P70 for anxiety, depression, and cognition. Both sexes tested.

This null finding challenges the assumption that adolescent cannabis exposure directly causes lasting psychological harm. If the behavioral deficits seen in human studies are not reproduced in controlled animal experiments, non-cannabinoid factors (social environment, other substance use, pre-existing vulnerabilities) may drive the human associations.

Null findings in well-designed animal studies are important because they control for the confounds that plague human observational research. If controlled cannabinoid exposure does not produce lasting behavioral changes, the human literature may be capturing correlation rather than causation.

Rat behavior may not fully model human psychiatric conditions. The abstinence period (to P70) may not be long enough. Cannabis smoke exposure methods may not replicate human consumption patterns. Only behavioral outcomes were measured, not neurochemical or structural changes.