DEAR DR. DONOHUE: How serious is bipolar disorder? Can you control it yourself? Is the brain lacking some element? — L.R.

A: Bipolar is a disorder in which people experience spells of deep depression alternating with spells of great energy and unbridled enthusiasm. It’s an emotional teeter-totter. In the high-energy phase, people feel invincible, are constantly on the go, can do with little sleep, have grandiose and unreasonable plans and are overly sociable. They become impulsive and make hasty and poor decisions. Sometimes they hallucinate, seeing things not present and hearing things not spoken. In the depressed phase, the opposite holds. People become reclusive, feel that all is hopeless, don’t want to get out of bed and are reluctant to interact with others. Those extremes are the two poles of bipolar disorder.

Yes, it is a serious illness. It can disrupt a person’s life.

Brain chemistry is involved, but the exact mechanisms are not completely understood. Genes have a major role too. Bipolar disorder runs in families.

People cannot control these mood swings by themselves. They will have times when the extremes of the two poles are not present but, predictably, the highs and lows return.

Medicines are most helpful in restoring stability to people’s lives. Lithium is a medicine with proven good results. There are others.