DALLAS — Grant Halliburton was handsome, artistic, bright, popular and loved.

He also suffered from bipolar disorder and depression. When he was 19, he jumped off a 10-story building to his death.

His mother, Vanita Halliburton, has gone over this tragedy again and again. If she knew now what she knew then, she believes the outcome might have been different than it was that awful day in November 2005. She created the Grant Halliburton Foundation in Dallas in the hope that the outcome will be different for others. The group teaches the signs of mental illness and puts people in touch with available resources.

It’s a crucial mission because, while experts agree that early intervention saves lives, most people wait years before getting help. The delay can be tragic.

“We were a typical family,” Halliburton says softly on the phone. “We were parents with reasonable intelligence and reasonable means to do whatever it might take to get our son well. And if we didn’t get this right, then what about the people who don’t have a clue or don’t pay attention to the signs or brush them off?”

The statistics, as Halliburton says, are shocking.

One in five Americans 18 or older has experienced a diagnosable mental illness or behavioral or emotional disorder in the course of a year, according to a 2010 national survey released by the Substance Abuse and Mental Health Services Administration.

The survey, of about 67,500 people 12 and older, shows that 5 percent of adults suffer from mental illness so severe that it limits major life activities.

About 8.7 million people have had serious thoughts of suicide. The survey shows 2.5 million planning suicide and 1.1 million actually attempting it.

According to the National Alliance on Mental Illness, suicide is the eighth leading cause of death overall in the United States and the third leading cause of death for people between the ages of 15 and 24.

The good news is that mental illness can be managed successfully with medication and therapy, experts agree. The bad news is that only about 4 in 10 people experiencing mental illness receive services, according to the SAMHSA report.

The average time between when symptoms appear and treatment begins is nine years.

Among the roadblocks to getting help are guilt over the idea that you or the person with the illness is at fault, confusion about what to do and resistance on the part of the loved one to acknowledge his illness, says Dr. Lloyd I. Sederer.

Sederer, a psychiatrist and medical director of the New York state office of mental health, wrote “The Family Guide to Mental Health Care” (W.W. Norton & Co., $25.95), a practical guide due out in April, which clarifies that mental illness is a physiological disorder that is no one’s fault.

“There are certain areas of the brain that look different in people afflicted with mental illness than in those individuals who are not,” Sederer says. “We have to set aside confusion, sadness, anger and despair and get on with what needs to be done.”

Sederer says once family members spot the signs, they should be direct when talking to a loved one they think might be suffering. “Describe to the person you love what you see going on. Be specific. Tell the person, ‘I have not lost confidence in you. I love you and believe in you. I know this is not who you are, this is not the person I’ve known for so long. My love for you insists we find help. I will be here to support you.’”