-- Comedian Rob Schneider's Twitter rant blaming Parkinson's drugs for Robin Williams' death has highlighted the delicate balance between the risks and benefits of the prescription drugs millions of people take every day.
In a series of tweets Monday, Schneider blasted the "evil pharmaceutical industry" for admitting that "100,000 people in the USA die a year from prescription drugs," some of which list suicide as a side effect.
But Parkinson's disease experts say Schneider is out of line.
"Suicide is of no more concern in patients with Parkinson's versus those who don't have Parkinson's," said Dr. Irene Richard, a professor of neurology and psychiatry at the University of Rochester Medical Center and a science adviser to the Michael J. Fox Foundation for Parkinson's Research.
In fact, a 2001 Howard University study found that people with Parkinson's are ten times less likely to commit suicide than the average person. Robin Williams' widow revealed after the comedian's death that Williams had been diagnosed with Parkinson's.
Parkinson's disease is a progressive condition of the nervous system marked by tremors and general difficulty with movement. It attacks the nerve cells that produce neurotransmitters associated with mood and, along with the shock of the diagnosis, can lead to depression, studies suggest.
More than 50 percent of people who receive a Parkinson's diagnosis develop clinical depression, according to Parkinson's Disease Foundation. The foundation notes that about 30 percent of patients reported being depressed even before their diagnosis and that antidepressants are often an effective treatment. Parkinson's medications like pramiprexole even have an antidepressant effect, according to the foundation.
However, some Parkinson's drugs do list an increased risk of suicide as a possible side effect.
For example, the U.S. Food and Drug Administration warns that patients taking either levodopa or SINEMET, two drugs commonly used to treat Parkinson's, "should be observed carefully for the development of depression with concomitant suicidal tendencies."
Some Parkinson's drugs have also been shown to increase impulsive behaviors that can lead to out-of-control gambling, sex addiction and other compulsive disorders. But Richard, who studies Parkinson's related depression, cautioned against linking impulsiveness to suicidal tendencies.
The only Parkinson's treatment that has an outright possible association with increased suicide risk is deep brain stimulation, Richard noted, a surgery where electrodes are implanted in the brain to control its electrical activity. Any candidate for such an operation would be carefully screened for history of depression and other mood disorders, Richard said.
Several prescription medications list suicide as a possible side effect -- a labeling requirement based on safety data, patient reports and other relevant information, according to the FDA.
"It is limited to those events for which there is some basis to believe there is a causal relationship between occurrence of an adverse event and the use of a drug," FDA spokeswoman Sandy Walsh told ABC News.
The agency is currently examining concerns about suicidal tendencies linked to a diverse list of medications, including some for asthma, controlling seizures and even one for quitting smoking. All antidepressants in the United States carry a warning that they are associated with an increased suicide risk in adults aged 18 to 24 during initial treatment, according to the National Institutes of Health.
So long as their depression is properly managed, James Beck, vice president of scientific affairs for the Parkinson's Disease Foundation, said that suicide shouldn't be a primary worry for the majority of Parkinson's patients. He added that if Schneider did not know the specifics of Williams' treatment, then his tweets were ill-informed and irresponsible.
"Williams had a lot of issues and it's hard to say what was going through his mind," said Beck, who was not involved in Williams' care. "I don't think you can blame his suicide on one particular thing."
Schneider's spokesman told ABC News that the comedian, who was a longtime friend of Williams', would not be commenting any further.