By the way, doctor: What are the side effects of lithium?

Q. What can you tell me about the side effects of lithium?

A. Lithium is a drug most often used to treat people with bipolar disorder (sometimes known as manic-depressive illness), a psychiatric disorder characterized by extreme shifts in mood, from excessively euphoric (mania) to desperately sad or hopeless (depression). In the manic phase, such individuals may be elated, require little sleep, or have inflated notions about themselves. In the depressive phase, they may have low energy, experience changes in eating or sleeping, or feel guilty, hopeless, or suicidal.