The bill eventually garnered widespread support because of the tenacity of Domenici, a father of eight, whose own struggle struck a chord in others.
Kennedy's sister Rosemary, who died in 2005 at the age 86, spent a life disabled and institutionalized after a lobotomy for mental illness nearly 60 years ago. His first wife, Joan, still wages a public battle with alcoholism.
The senator's son, Rep. Patrick J. Kennedy, D-R.I., who sponsored the House version of the parity bill, has faced bouts of prescription drug abuse and depression.
"There isn't an individual or a family that has been spared the impact of these devastating illnesses," Rep. Kennedy said in an e-mail. "To deny coverage, when proven and available treatments can make such a positive difference in a person's life and their family's life, is beyond infuriating."
Just recently, Domenici was diagnosed with frontotemporal lobar degeneration, or Pick's disease, which progressively affects brain functions like organization, decision-making and control of mood and behavior.
The six-term senator retires in 2009, but not without leaving a historic legacy for 113 million Americans under employer-sponsored insurance plans who are expected to benefit from the legislation.
"This moves the ball tremendously," said Domenici. "I'm a pretty passionate guy, and there's a certain amount of pleasure in doing things that are hard to do."
Today, about 58 million Americans have a diagnosable mental disorder. Mental illness has also been associated with more than 30,000 suicides each year. An estimated 16 percent of all inmates suffer from mental illness.
The new law does not mandate group plans to provide mental health coverage, but requires insurance plans that offer mental health coverage to do so on a par with physical illnesses. Only companies with more than 50 employees must comply.
Before the 1980s, Domenici hadn't paid much attention to mental health care -- that is until his daughter, Clare, now 46, was diagnosed with atypical schizophrenia after her first year in college. She struggled with her focus, had bouts of anxiety and her personality began to change.
"For a long period of time, my parents were trying to determine what was the matter with her," younger sister Paula Domenici told ABCNews.com. "They were mystified."
Since then, her sister has gone on and off a cluster of medications – many with adverse side effects, such as weight gain.
"She had been a star athlete and a good student with lots of boyfriends," said Paula Domenici, 41, a psychologist who works with veterans in Bethesda, Md. "To see such a transformation was shocking. It's a slow evolution and sad for families to have to acknowledge."
Do you have more information about this topic? If so, please click here to contact the editors of ABC News.
