Low-Dose THC Improved Memory in Aging Mice. Higher Doses Impaired It in Young Ones.

The well-known cognitive impairment from THC — disrupted short-term memory, slower processing — turns out to be only half the story. Recent animal research showed that chronic low-dose THC administration to old mice actually improved neurological function, promoted hippocampal neurogenesis, and protected against inflammation-induced cognitive damage.

The authors argue this isn't contradictory — it's hormesis, a biological pattern where a substance produces opposite effects at low versus high doses. At the doses that impair young brains, THC overwhelms endocannabinoid signaling. But at very low doses in aging brains where the endocannabinoid system has naturally declined, THC may restore signaling to a functional range.

The review also highlights evidence that low-dose THC prevented neurodegenerative processes in animal models of Alzheimer's disease and restored memory in aging mice — findings that would seem impossible based only on the impairment literature.

This paper challenges the straightforward narrative that THC is bad for your brain. It's not saying THC is good for your brain either — it's saying the answer depends on dose, age, and baseline endocannabinoid function. That's a much more nuanced and scientifically accurate picture.

The hormesis framework is important because it explains why studies seem to contradict each other. A study showing THC impairs memory in college students and a study showing low-dose THC restores memory in elderly mice aren't actually contradictory — they're measuring different parts of the same dose-response curve in different biological contexts.