Lithium

Lithium prevents unipolar and bipolar depression.
Lithium prevents suicides in patients and in the general population at minuscule dosages in the water supply.
Lithium enhances the positive effects of virtually all the other mood stabilizers and atypical antipsychotics on mood and behavior.
Lithium increases the volume of the hippocampus.
Lithium prevents or reverses cortical gray matter and white matter tract deficits.
Lithium normalizes circadian rhythm abnormalities that regularly occur in patients with bipolar disorder.
Lithium has immune-modulating and antiviral effects.
Lithium increases the length of telomeres shortened by episodes, stress, and aging, yielding fewer senescent cells, thus promoting better physical and psychiatric health.
Compared to placebo, low-dose lithium prevents or slows memory deterioration in mild cognitive impairment (over 1 year in one study and over 2 years in another).
Clinical dosages of lithium in the treatment of bipolar disorder reduce the incidence of a diagnosis of dementia in old age.
Lithium prolongs life expectancy and reduces the incidence of cardiovascular and all-cause mortality.