It is proposed that lithium’s therapeutic effects occur indirectly by augmenting a cascade of protective “fail-safe” pathways pre-configured to activate in response to a dangerous low cell [Mg++] situation, eg, posttraumatic brain injury, alongside relative cell adenosine triphosphate depletion. Lithium activates cell protection, as it neatly mimics a lowered intracellular [Mg++] level.