One in 12 stroke survivors thought about suicide or that they would be better off dead, a troubling U.S. survey reveals. That's more than those with other health problems such as heart attacks or cancer, and it suggests that depression after stroke is more serious than many had realized.

"It was surprising" and shows a need for more treatment, said the study's leader, Dr. Amytis Towfighi of the University of Southern California in Los Angeles. "When patients have their depression treated they're more motivated to take their medication, do therapy and live a full life."

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In his book Stroke of Luck, actor Kirk Douglas said he was affected by suicidal depression following a stroke. About 8 per cent of U.S. stroke survivors reported they had been bothered by thoughts they'd be better off dead or considered hurting themselves. (Reed Saxon/Associated Press)

The study was discussed Thursday at an American Stroke Association conference in Honolulu.

More than 6 million Americans have had a stroke; about 800,000 occur each year in the U.S. Studies suggest that up to a third of stroke survivors develop depression, but few have looked at suicidal thoughts — one sign of how serious it is.

"It's not necessarily active suicidal thoughts with a plan, but perhaps wishing you hadn't survived the event," Towfighi explained.

She used the National Health and Nutrition Surveys, a U.S. government project that gives check-ups and questionnaires to a representative sample of adults. More than 17,000 people were surveyed from 2005 through 2010.

They included 678 who had suffered a stroke; 758 who had had a heart attack; 1,242 with cancer, and 1,991 with diabetes. Researchers don't know how long ago these problems occurred of if people were still being treated for them.

They were asked a question that many studies use to gauge suicidal thinking: "Over the last two weeks, how often have you been bothered by thoughts that you would be better off dead, or of hurting yourself?"

About 8 per cent of stroke survivors reported such thoughts, compared to 6 per cent of heart attack survivors, 5 per cent of those with diabetes and 4 per cent with cancer.

Suicidal thoughts were more likely in people who scored high on depression tests, were younger, overweight, less educated, poor, female or unmarried.

Depression may develop partly because strokes damage the very thing that controls mood — the brain, said a neurologist with no role in the study, Dr. Brian Silver of Brown University and Rhode Island Hospital.

"It's not necessarily the reaction to the disease … it's also the disease itself that is causing the depression," by releasing harmful chemicals that can trigger it, he said.

Suicidal thinking is a well-known problem, but this study "puts a number on it" and shows the need to watch for and treat it, Silver said.