The city of San Francisco—and indeed the whole nation—was saddened earlier this month to learn of the death of comedian Robin Williams, who had been suffering from depression. We later learned that Williams was also battling the early stages of Parkinson’s disease.
The comorbidity between depression and Parkinson’s disease is no surprise to clinicians and researchers involved with psychiatric and movement disorders. Indeed, a recent study conducted by Northwestern University investigators in collaboration with the National Parkinson’s Foundation found that depression is the most prevalent non-motor symptom of Parkinson’s. “Nearly a quarter of the people in the study reported symptoms consistent with depression,” said Danny Bega, first author of the study.
The relationship is also no surprise to clinicians and researchers in the deep-brain stimulation field. In fact, some of the early studies of DBS for depression came about precisely because of the participation of DBS Parkinson’s patients who were also experiencing mood disorders. The close proximity of DBS targets for Parkinson’s and depression may be indicative of a common cause. It may also motivate clinicians to devise DBS therapies that address both conditions simultaneously.
Tammy Hershey from Washington University has studied the side effects that can result from improper placement of a DBS lead or improper choice of contact and found that mood disturbances can often result from STN stimulation for Parkinson’s [NBR Jun12 p7]. There is wide individual variability in optimal placement and the effect of medication levels only compounds the complexity. Whether or not there is a common etiology between movement and psychiatric disorders, it has become increasingly important for clinicians to fine-tune the placement of DBS leads for each individual and to test the choice of contacts and stimulation parameters before setting on a therapeutic regimen.
While the precise cause of Parkinson’s disease is still not perfectly understood, it is safe to say that we know much more about it because of our experience treating thousands of individuals with DBS than we would have known without the help of these pioneering users. We believe the same will be true about DBS and psychiatric disorders years from now, provided regulators allow this to come to pass.
As Robin WIlliams reminds us, major depression is a life-threatening disease and available pharmacological therapies fail to help a large percentage of sufferers. We would not expect the FDA to pull these drugs off the market just because they can’t help everybody. Similarly, we should not expect the FDA to keep neuromodulation therapies for depression off the market just because they can’t help all of the people that drugs can’t help.
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