GSK3B

In one line: An enzyme that low-dose lithium calms — possibly protecting the ageing brain.

GSK3B is an enzyme involved in many cellular processes; calming it appears to protect neurons and switch on cellular cleanup. Tiny doses of lithium (far below psychiatric doses) inhibit it, which may be why regions with more natural lithium in their water show slightly lower death and suicide rates. Very early evidence — intriguing, not established.