In situations with low external stimulation, manic patients often present rapid declines in vigilance, with microsleeps occurring even in the 1st min of EEG recordings (lability of vigilance regulation). We postulate that manic symptoms creating a high level of external stimulation serve to stabilize vigilance. Theoretical arguments and empirical results are presented, showing that both mania and ADHD should be interpreted as vigilance autostabilization syndromes. The therapeutic effects of psychostimulants can be explained by their vigilance-stabilizing properties. They are well proven for ADHD and have repeatedly been shown to have a paradoxical effect in manic patients. The proposed concept opens new approaches for the treatment of acute mania.