ONLY 61 percent of Americans think it appropriate to tell family members about a mental illness diagnosis, according to a recent study commissioned by the New York City Metro chapter of the National Alliance on Mental Illness. Just 43 percent approve of telling friends about a diagnosis, and just 13 percent of telling co-workers.

That stigma has prompted the chapter to begin a public service campaign featuring a commercial, shot in black-and-white along the East River in Lower Manhattan, that opens on a close-up of Michael Thompson.

“It was my older brother, Tom,” says Mr. Thompson, who speaks to an off-camera interviewer in the style of a documentary. “When I would visit him occasionally, he would talk about things that didn’t make sense to me. Bottom line, I got a call.”

Mr. Thompson sighs, shakes his head as if to banish a thought, purses his lips. A tear rolls down his cheek. “And — and my brother killed himself,” he says.