Clinical depression is an alternate term for major depression, a serious mental health concern that affects relatively large segments of the U.S. population. This ailment is known for its potential to increase the risks for the onset of other dangerous health problems. In a study published in October 2013 in the journal Neurology, a team of Taiwanese researchers looked at major depression as a risk factor for the onset of Parkinson’s disease, a progressive disorder marked by damaging changes in brain and body function. These researchers concluded that, separate from any other issues, major depression increases an individual’s long-term Parkinson’s risks.
Major Depression Basics
People with major depression experience bouts of overlapping symptoms that collectively reduce the ability to maintain a sense of mental well-being, participate in a daily routine or uphold personal or social responsibilities. Although the symptoms vary from person to person, well-known effects of the disorder include a strongly downcast overall mood, heightened levels of sadness, helplessness or other potentially debilitating emotional states, an unusual tendency to overeat or skip meals, an unusual tendency to oversleep or experience sleeplessness, difficulty thinking clearly or forming judgments, unusual levels of frustration or agitation, a reduced sensitivity to pleasure, and a substantial drop in energy levels. Although all diagnosable cases of major depression cause significant life disruption, some people develop relatively extreme depression-related symptoms, while others develop relatively moderate symptoms.
Parkinson’s Disease Basics
Parkinson’s disease is classified as a motor system disorder. All disorders with this classification involve changes in the brain’s usual function stemming from the untimely death of the cells that normally help control body movement. In mental health terms, Parkinson’s disease is one of the known potential causes of dementia, a condition characterized by a decline in the brain abilities that form the basis for unique human consciousness. Common observable symptoms of the disease include uncontrollable tremors in the limbs or face, unusual difficulty getting the body to move quickly, an inability to fully coordinate body movement or control body posture, and uncharacteristic muscle stiffness. Affected individuals typically develop minor forms of these symptoms that grow worse over years or decades.
Doctors have long known that depression and Parkinson’s disease appear together with considerable frequency. They also know that the presence of one condition can worsen the effects of the other. For instance, depressed people with Parkinson’s disease commonly have more symptoms of emotional debilitation, anxiety and poor mental clarity than depressed people unaffected by Parkinson’s disease. Conversely, Parkinson’s-affected individuals with diagnosable major depression commonly experience greater problems with movement control than Parkinson’s-affected individuals without diagnosable depression.
In the study published in Neurology, researchers from several Taiwanese institutions conducted a nationwide assessment of major depression as a potential risk factor the development of Parkinson’s disease. This assessment included 4,634 individuals diagnosed with depression, as well as a comparison group of 18,544 individuals unaffected by depression. Over a 10-year period, the researchers examined both of these groups to see how many people developed Parkinson’s disease. In order to make sure that they didn’t include people who became depressed after a Parkinson’s disease diagnosis, they excluded all individuals who developed both depression and Parkinson’s disease within a two- to five-year time span.
After 10 years, 1.4 percent of the study participants diagnosed with major depression had developed Parkinson’s disease. In contrast, only 0.5 percent of the study participants unaffected by major depression developed Parkinson’s. Obviously, these low rates indicate that Parkinson’s disease is a relatively uncommon condition. However, they also indicate that people with major depression develop Parkinson’s disease fully three times more often than the larger depression-free population. To confirm this finding, the researchers systematically accounted for the effects of all other factors that could increase a person’s Parkinson’s risks, including diabetes, gender-specific influences, age-specific influences and high blood pressure. Even after making these adjustments, they concluded that major depression remains as an independent Parkinson’s disease risk factor.
The authors of the study published in Neurology note that their findings don’t mean that major depression “causes” Parkinson’s disease. Instead, the presence of major depression statistically increases the odds that Parkinson’s disease will occur. Depression-related Parkinson’s disease risks are likely highest in elderly adults and people who have treatment-resistant depression that doesn’t respond well to antidepressant medications.