First-degree relatives of people
with Parkinson's disease appear to be at increased risk for developing depression
and anxiety disorders
First-degree relatives of people with Parkinson's disease
appear to be at increased risk for developing depression and anxiety disorders,
according to an article in the December issue of the Archives of General Psychiatry.
The risk is particularly increased in families of patients
who develop Parkinson's disease before age 75 years. The research was conducted
at Mayo Clinic, Rochester, MN.
Researchers evaluated 1,000 first-degree relatives of
162 patients with Parkinson's disease in the county in which the medical center
is located. In addition, they evaluated 850 first-degree relatives of 147 matched
controls from the same population.
The investigators used the medical records-linkage system
of the Rochester Epidemiology Project to identify subjects with Parkinson's disease
and the control subjects and to obtain clinical information about psychiatric
diseases for relatives in both groups who lived part or all of their lives in
Olmsted County. Housed at Mayo Clinic, the Rochester Epidemiology Project is one
of the largest long-term, integrated databases of patient records in the world.
Documentation of psychiatric disorders for relatives
was obtained by a direct interview whenever possible (or by an interview with
their proxy for those who had died prior to the study or were incapacitated),
and through a review of their medical record. Psychiatric disorders in the medical
records were defined using published clinical criteria or physician diagnosis.
Diagnoses were verified by a neurologist and a psychiatrist at Mayo Clinic who
were not told whether the record was from a relative of a patient with Parkinson's
disease or from a relative of a control subject.
The results were consistent in analyses that adjusted
for type of interview, excluded relatives who developed parkinsonism, or excluded
relatives who developed both a depressive disorder and an anxiety disorder.
"Studies by our group and others have shown that
relatives of patients with Parkinson's disease have an increased risk of Parkinson's
disease," explains Walter Rocca, MD, senior author of the study and a Mayo
Clinic neurologist and epidemiologist. "Recently, we showed they also have
increased risk of essential tremor and of cognitive impairment or dementia. However,
their risk of psychiatric disorders was unknown.
"Because many patients with Parkinson's disease
develop anxiety and depression after and even before the onset of the disease,
we explored whether this tendency was present to a greater extent in family members
of people with Parkinson's disease compared with people without the disease. We
found that, indeed, relatives of patients with Parkinson's disease are at increased
risk for anxiety and depressive disorders, which suggests a genetic or other relationship
between those disorders and Parkinson's disease."
Rocca emphasized that the familial susceptibility factors
may be genetic, environmental or a combination of the two, and that further research
is needed to determine their exact nature.
The current study is the first large population-based
study to show that Parkinson's disease and psychiatric disorders may share familial
factors that make a person susceptible to developing one or both. An important
methodological feature of the study is that researchers assessed each family member
individually, rather than having one relative provide information for the entire
family.
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