Patients with bipolar disorder may be more expected to suffer from Parkinson's disease. Scientists exposed the association between the two after they assessed the outcomes of seven research studies involving 4.3million participants. They found out that patients having mood disorder were larger in number (i.e. three times) than Parkinson’s and were more likely to finish up with Parkinson's, as per the findings.

The researchers amended their observations to take into consideration Parkinson factors including medication history, age, sex, as well as history of diseases and injuries having an effect on the brain, all of which could control a person's risk of developing Parkinson's. After this amendment, they observed that participants were approximately seven times more expected to undergo Parkinson's if they had a diagnosis of bipolar disorder at the beginning of the study, as compared with those who fail to suffer from bipolar disorder. It also appears that the rigorousness of the bipolar disorder impacted the level of risk; individuals who had to go the hospital owing to bipolar disorder most often had a greater risk of developing Parkinson's at a later phase in their lives.

Another implication is that bipolar disorder might lower down the levels of dopamine. And it is observed that a deficiency in the levels of dopamine is the major reason behind the occurrence of Parkinson's. Individuals with bipolar disorder had a greater risk of Parkinsonism than individuals without the disorder, and this was found in a longitudinal study which was conducted in Taiwan.

A bipolar identification upped the possibility of Parkinson’s disease dementia by almost seven times, Mu-Hong Chen, MD, PhD, of Taipei Veterans General Hospital in Taiwan, and colleagues reported in Neurology. The inclination was quite noteworthy even in adults younger than the age of 65 years, as well as the incidence of psychiatric accesses for manic/mixed as well as depressive incidents linked with the risk of Parkinson's disease.

"Previous research studies have found out a link between depression as well as Parkinson's disease, but few research studies have explored whether there is an association between bipolar disorder and Parkinsonism," Chen said in a statement.

What Parkinson's as well as bipolar disorder connection is unclear, but "could involve genetic alterations, inflammatory processes, or troubles with the transmission of signals between brain cells," he implied. "If we could discover the basic cause of this link, which could most likely help us widen treatments that could assist both conditions."

Mood disorders are the most familiar psychiatric disorders related with Parkinson's as well as may present before or following the commencement of motor signs, noted Gregory Pontone, MD, MHS, of the Johns Hopkins University School of Medicine in Baltimore, as well as Giacomo Koch, MD, PhD, of the Santa Lucia Foundation in Rome, in an additional perspective.

"Even though both major depression as well as bipolar disorder is mood disorders that may be illustrated by recurrent episodes of low mood (depression), bipolar disorder also necessitates the presence of greater than 1 manic or mixed episode," they wrote. "Regardless of the clinical similarities as well as the prospect of etiologic overlap, major depression and bipolar disorder have conflicting genetic risk."

In this study, Chen and co-authors carried out study on 56,340 adults in the Taiwan National Health Insurance Research Database who had been diagnosed with bipolar disorder from 2001 to 2009 and who had no history of Parkinson's disease, evaluating them with 225,360 age- as well as sex-matched controls. They followed both groups until December 31, 2011.

The average age in the study was approximately 40. The occurrence of cerebrovascular disorders, traumatic brain injury, hypertension, dyslipidemia, as well as diabetes was found to be comparable in each group.

During the research study, about 0.7% of individuals with bipolar disorder suffered from Parkinson's disease, as compared to 0.1% of controls (P< 0.001). After adjusting for demographic data as well as medical history, individuals with bipolar disorder found a hazard ratio of 6.78 for developing Parkinsonism as compared with controls (95% CI 5.74-8.02). The relation was found both in individuals below the age of 65 years (HR 12.02, 95% CI 9.33-15.51) as well as in those 65 and older (HR 3.87, 95% CI 3.05-4.09).

On the whole, individuals suffering from bipolar disorder were diagnosed with Parkinson's disease at a younger age (64.25 years) as compared to controls (72.99 years, P< 0.001).

The probability of Parkinson's increased with the number of psychiatric admissions per year. In total, bipolar patients who were hospitalized more than twice a year were about 6 times more expected to develop Parkinson's disease as compared to those hospitalized less than once a year.

Trends remained even subsequent to a series of sensitivity analyses, such as one to lessen the probability that iatrogenic Parkinsonism was produced by mood-stabilizing treatments such as antipsychotics.

The observations must be viewed in the circumstance of numerous limitations, Pontone and Koch noted. In research studies like this, it's hard to recognize when the pathologic process of Parkinson's initiates. "For example, a lot of individuals believe that the disease is active several years or even decades prior to the onset of motor signs, in which case bipolar disorder or mood dysregulation resembling bipolar disorder may more suitably be viewed as an early sign of Parkinson's disease," they wrote.

In addition, genetic factors could play a key role in the relationship between bipolar disorder as well as Parkinson's disease, they noted. And despite regulating for antipsychotic medicines, the risk that some Parkinson's disease identified in this study was in fact drug-induced Parkinsonism remains a option, they said.

"Mood and movement are associated at the level of treatment in that antipsychotic as well as mood-stabilizing treatments over and over again lead to movement disorders, such as tardive dyskinesia, tremor, acute dystonia, and parkinsonism," Pontone as well as Koch observed.

The nature of this association may be key: "In the case of bipolar disorder as a risk factor for Parkinson's disease, evaluating the underlying reason behind this relationship might permit the early recognition of Parkinson's disease as well as inform the development of disease-modifying therapies that could gain both conditions," they wrote.