In 2006, he had sought treatment for alcohol addiction at the Hazelden center in Springbrook, Ore., according to published reports.
Despite Williams' well-documented personal battles, mental health experts point to major strides in recent decades in the treatment of people who struggle with depression and substance abuse, which are often twin afflictions.
The most effective treatments are medication and talk therapy, said Dr. Jeff Borenstein, president and CEO of the Brain and Behavior Research Foundation in New York City. This dual approach works for most people who are dealing with depression, he said.
"It's extremely difficult to live with depression. The pain is described by people as the worst pain possible. But the majority of people treated for depression get better," he said.
Surprisingly, Borenstein added, there's still a stigma that's often attached by some to depression. But, it's just as much a disease -- not a sign of a personal shortcoming -- as a physical ailment like cancer or heart disease, he said.
"Unfortunately, in our society that [stigma] is still tolerated by some people," Borenstein said. "We no longer accept prejudice against race or religion or sexual orientation, but there are still people who have this prejudice when it's a psychiatric condition," he said.
What's also troubling, Borenstein added, is that too many people with depression don't seek treatment. "That is a major problem in our country," he said. "It's important that people be aware of depression so that they can encourage a loved one to seek treatment."
For many of Williams' fans, his signature talent was his manic, brilliant brand of comedy. But he also tackled many dramatic film roles, including ones in "Awakenings," "Dead Poets Society"
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