WHAT IS A STROKE?

Strokes are a leading cause of death worldwide and affect almost 800,000 Americans each year. The World Health Organization estimates that about 1 in 4 people will have a stroke at some point in their lives.

Fetterman had the most common kind of stroke, caused by clots that block a blood vessel to the brain. The less common kind is due to a a burst or bleeding blood vessel.

Brain cells can begin to die within minutes. There can be one-sided paralysis and problems with speech and cognition, but quick treatment with clot-busting medication can lead to a full or partial recovery.

Fetterman, 53, had a serious stroke last May, and went on to win a highly publicized Senate race against GOP challenger Mehmet Oz. The aftereffects include difficulty processing spoken conversation, but his doctor has said his thinking ability is intact.

WHAT IS DEPRESSION?

Depression is a mood disorder that can cause intense feelings of persistent sadness, anxiety and hopelessness. It is thought to impair the function of chemicals that carry messages between brain cells.

Depression affects about 16 million Americans every year, or about 1 in 6 adults globally.

Fetterman had bouts of depression before his stroke and his office announced Thursday that he had checked himself into Walter Reed National Military Medical Center to treat his depression, which worsened recently.

Depression is typically treated with medication and psychotherapy. Studies have shown both can help post-stroke depression, but more research is needed to determine which antidepressants are most effective after strokes, according to guidance from the American Heart Association and American Stroke Association.

IS THERE A LINK BETWEEN STROKES AND DEPRESSION?

Depression occurs after a stroke in about 1 in 3 patients, said Dr. Will Cronenwett, psychiatry chief at Northwestern University’s Feinberg medical school.

There may be a biological reason, with some evidence suggesting that strokes might cause brain changes that lead to thinking difficulties affecting how people perceive the world, and that in turn could lead to depression, Cronenwett said.

Strokes can also have a psychological impact, making it hard for some people to accept that they may have new limitations. In some people, that adjustment can lead to depression.

“Depression doesn’t have to happen immediately after a stroke; it can happen years later. But living as a stroke survivor does raise your risk for having depressive episodes,’’ Cronenwett said.