Dopamine and its Role in Parkinsons Disease - Research Paper Example

Dopamine and its Role in Parkinson’s Disease Parkinson’s disease (PD) is a chronic disease that debilitates an individual over time. Beyond the physical issues for PD there are also mental and emotional challenges. Central to these other issues is depression, dementia, psychosis and personality disorders. Depression is one of the most prominent of the disorders with 45% of people with PD experiencing it (Lemke 9). In the article, “Dopamine Agonists in the Treatment of Non-Motor Symptoms of Parkinson’s Disease: Depression” by M.R. Lemke, a better understanding of how dopamine works in PD is presented. 1 Dopamine and Depression In the section on dopamine and depression, Lemke gives an overview of the research that has been conducted regarding the use of dopamine and depression. The author sites several studies. The first study consisted of 1,023 patients and found that depression was a part of PD. Another study suggested that the area in the brain that is responsible for feelings of joy and pleasure are also the area responsible for “motivation, drive and activation” (9); this area is in the limbic system and is called the dopaminergic reward mechanism (9). The study suggested that when this area is damaged, it can lead to “loss of motivation, apathy and avolition” (9). Two studies focused on the neural reason for abnormal emotional behavior. The first of these two studied abnormal behavior and the physiologic effects of dopaminergic therapy on the amygdala of the brain. This study tested 20 patients 10 with PD and a control group of “normal controls patients” (9). The patients were asked to look at two facial expressions and chose the one that matched a target expression. In the control task, they were supposed to match one of two geometric shapes. All patients were able to improve their performance once he drug was administered (10). The second of these studies used CRTI-32 positron emission topography which is an “invivo marker” for dopamine and noradrenalin transporter to identify the differences between patients with PD and those without it. They used a total of 20 patients, eight who were depressed and 12 who were not depressed. They tested both groups on the Beck Depression Inventory and found that patients who were depressed scored higher for depression and anxiety than those who were not depressed. Both groups received medication. They found that the depressed patients also had lower CRTI-32 binding than those who were not depressed (10). The researchers in this study stated that there appeared to be a link between depression and anxiety in PD. According to Lemke, these studies proved that dopaminergic treatment for PD was important and that there was a correlation between PD and depression. 1.1 Dopamine Agonists and Depression According to Lemke, dopamine agonists work on the dopaminergic systems of the body (10). Because they work directly on these areas, they may be responsible for mood behavior. One dopamine agonist, pramipexole, was studied by other researchers and found to react as an anti-depressant for bipolar disease and treatment-resistant depression (10). Several studies in this study showed that patients who took pramipexole performed better and were less depressed than those who did not take it (11). 1.2 Anhedonia and Depression Anhedonia is another agonist that has had positive effects on depression with PD patiens and it has also affected any motor alterations (11). Several studies were quoted in Lemke’s article that used this agonist. All of the other studies found that patients with PD were helped via the use of agonists by controlling depression. Lemke concluded that PD patients with depression “might” benefit from a global approach to the disease that included dopamine agonists because they seemed to reduce motor complications and symptoms of depression. By using an agonists the regimen of drugs could be lessened and would stop any side effects from the anti-depressant medications that the patients may be taking. 2 Article, “Depression in Patients with Parkinson’s Disease” by Jeffrey L. Cummings, Agustus S. Rose and Donna L. Masterman International Journal of Geriatric Psychiatry. 14.9 (1999): 711-718. This article was the second one on the list that Lemke used to support her article. The authors in this article began by stating that PD is progressive and disabling and older people are most affected by it. However, there is controversy over the rate of depression in these patients; in other words, no one really knows the percentage of patients who have depression that is attributed to PD. The researchers stated that there were two risk factors for depression and they were that the patient was diagnosed with PD before the age of 55 or they had PD in their family history. The authors did not conduct their own study but presented several studies that were specific to depression in PD. Although depression seems to be seen in about 40% of patients, the authors stated that it is undertreated (717). Usually, patients with PD are elderly and doctors give them a range of medication instead of concentrating on depression symptoms. They suggest that serotonin uptake inhibitors are a better fit for PD patients than trycyclic antidepressants (TCAS) because they have less side effects and create less risk to the patient. The researchers concluded by stating that there needs to be more study of depression in PD. 3 Article, Anxiety Disorders and Depressive Disorders Preceding Parkinson’s Disease: A Case Control Study” Shiba, Mitsura et al. “Anxiety Disorders and Depressive Disorders Preceding Parkinson’s Disease: A Case Control Study”. Movement Disorders, 15.4 (2000): 669-677. DOI: 10.1002/1531-8257(200007)15:43.0.CO;2-5 This article was the first on the list of articles that Lemke used for support of her research. Mitsura Siba et al (2000) studied the association between “preceding psychiatric disorders” and PD (669). Their research identified 196 subjects with PD who had PT between the years 1976 and 1995. They were able to receive the full medical records of these patients to try and identify any preceding psychiatric disorders. They were able to gain access to these records through the Rochester Epidemiology Project records-linkage system (669). They reviewed the database to find any patients with any level of Parkinson’s. The researchers looked for those patients who had the disease for five, 10 or 20 years (670). They only revied those patients who had four PD symptoms: rest tremor, brady kenesia, rigidity and impaired postural reflexes (670). 3.1 Results The results of their study showed that there were many preceding psychiatric disorders that happened prior to the diagnosis of PD. They found that the most significant psychiatric disorder was anxiety and that this had occurred prior to the 10 or 20 year old diagnosis. They also found that the longer that people had PD, the more motor challenges became an issue in addition to the anxiety disorders. However, the patients could only be classified as having an anxiety disorder not otherwise specified according to the DSM-IV criteria information (672). 4 Critique of Articles Lemke’s article was the lead article and it was very disappointing. This reader was waiting for her own study to begin but was disappointed because she only took the information from several other studies. The other studies that were chosen were ones with very limited information. As an example, two of the studies she chose only had 20 participants which did not seem like enough of a sample to gain real understanding of depression in PD. The study did not seem to really delve into whether depression was a symptom of PD or if it was because the individual had PD over a period of time. It seems that all chronic disease carries some depression because the individual suffers from it over time. Many people that this researcher knows who have chronic diseases are depressed a lot of the time. Lemke made the assumption that depression was a symptom of PD but it may be a consequence of having PD. As an example, a person who has PD over a long period of time and experiences the same pain or instability in their daily life would probably be more susceptible to depression more of the time than someone without chronic disease. Since the disease is debilitating, an individual would see more and more of their life being changed because their illness would take over. 4.1 Reliability According to Georgetown University, reliability in psychological research means that a study actually measures what it is supposed to measure. In this case, the researchers set out to study depression and its relationship to PD and they found that there may be some validity in the idea that there is a correlation between PD and depression. Also, the research must yield consistent results. In looking at all the studies that were quoted and Lemke’s study, they were all consistent. In each study they found patients with PD that were depressed and this happened for 40-45% of the patients. Because this was consistent and measured what it was supposed to, it can be said that there was reliability to these studies. 4.2 Validity When a study is said to be valid, it is said to be well-grounded in theory and is peer reviewed. On the one had, this article could be said to be valid but a question comes to mind when there are only a few patients that were studied. As an example, when there are only 20 or so people in a study it would seem that the study is not as valid as if there were 1,000 or more. It would seem that the more people within a study, the better able the researcher would be able to say that whatever they were studying really was valid. Timothy Meline, in his article, “What Makes a Good Journal Article” states that there are several criteria for a good journal article. These criteria include that the article is grounded in theory, it is connected to previous work in the literature review, there is a stated hypothesis, the conclusion is within the boundaries of the findings, the study helps to resolve an original problem and there are practical and theoretical implications drawn from the study (2). According to this information, the study by Lemke is not a very good article. It meets the criteria of being connected to previous work, but it does not meet the criteria for a theory grounded in theory, it does not have a stated hypothesis and it does not really resolve an original problem since a problem was not really stated. Therefore, this is not a very good article in this criteria. In this researcher’s opinion, the article did not give enough information. Usually academic journal articles give information in the beginning of the article about the topic, they provide a short or long literature review, and then they conduct their own study. Lemke took information from other people and gave her opinion on it at the end. Much of the language that was used was difficult to understand because it was very technical (e.g. the discussion of dopaminergic mechanisms, mesolimbic dopaminergic and so forth) and unless the reader had background in medicine it would not seem to be easy for the reader to understand. Also, the idea of dopamine agonists was difficult because it was not defined in this article. The article by Cummings, Rose and Masterman was more interesting because they used a database that had already been created for patients and they were able to choose patients with PD. This gave them a broader perspective, in this researcher’s opinion, than Lemke’s perspective. In conclusion, it would seem that there may be a connection between the use of dopamine agonists for PD to help depression since it helps many other mood disorders. There should be other studies done that deal specifically with the idea of depression as it effects PD. There should be studies conducted to decide whether depression is a natural progression in someone who has PD or if it is something that happens because they have the disease for such a long period of time. Many people are prone to depression whether they have PD or not and it would have been interesting to know whether the people they reviewed had a history of depression before they were diagnosed with PD. This would perhaps give a better understanding as to the connection to PD and why so many people seem to be depressed. Future research may also include information about the disease so that the lay person reading the article could gain more information about PD and its symptoms, and then understand how depression is linked to it. Works Cited Cummings, Jeffrey L., Rose, Agustus S., and Masterman, Donna L. “Depression in Patients with Parkinson’s Disease”. International Journal of Geriatric Psychiatry. 14.9 (1999): 711-718. Georgetown University. “Validity and Reliability.” Department of Psychology. 31 May 2011. http://psychology.georgetown.edu/resources/researchmethods/research/8304.html Lemke, M.R. “Dopamine Agonists in the Treatment o Non-Motor Symptoms of Parkinson’s Disease: Deprssion. European Journal of Neurology, 2.15, (2008): doi: 10.1111/j.1468-1331.2008.02213.x Meline, Timothy. “What Makes a Good Journal Article?” TEJAS Volume XXXI 2008 Texas Journal of Audiology and Speech-Language Pathology. (2008): 5-6. 31 May 2011. http://www.txsha.org/_pdf/TEJAS/2008/02b%20Journal%20Article.pdf Shiba, Mitsura et al. “Anxiety Disorders and Depressive Disorders Preceding Parkinson’s Disease: A Case Control Study”. Movement Disorders, 15.4 (2000): 669-677. DOI: 10.1002/1531-8257(200007)15:43.0.CO;2-5 Read More