Association Between Bipolar Disorder and Parkinson's Disease

Bipolar disorder and Parkinson's disease are two distinct neurological conditions that share common features related to dopaminergic dysfunction. This article presents a comprehensive review of the existing literature to investigate the association between bipolar disorder and Parkinson's disease, focusing on the dopaminergic hypothesis and potential therapeutic options. The dopaminergic hypothesis suggests that both bipolar disorder and Parkinson's disease involve impairments in the nigrostriatal or mesolimbic dopaminergic pathways. Studies have demonstrated alterations in dopamine regulation during manic and depressive phases of bipolar disorder. Similarly, Parkinson's disease is characterized by the loss of dopaminergic neurons in the substantia nigra, resulting in motor symptoms. Recent analyses have highlighted a predisposition to Parkinson's disease in individuals with bipolar disorder. Longitudinal studies and meta-analyses have demonstrated an increased risk of developing Parkinson's disease in patients with bipolar disorder. However, differentiating idiopathic Parkinson's disease from parkinsonism induced by medications used in bipolar disorder can be challenging. Dopamine transporter (DAT) scans can aid in making a differential diagnosis. Treatment options for patients with both bipolar disorder and Parkinson's disease are limited. Neuroleptics, commonly used to manage psychotic symptoms in Parkinson's disease, may worsen motor symptoms and have limitations in bipolar disorder patients. Clozapine has shown efficacy in treating psychosis without worsening motor symptoms. Pimavanserin, an inverse agonist of the 5-HT2A receptor can offer new opportunities. However, its efficacy in bipolar disorder patients with Parkinson's disease remains unexplored. In conclusion, the association between bipolar disorder and Parkinson's disease is supported by the involvement of the dopaminergic system in both conditions. The identification of shared mechanisms opens new avenues for potential therapeutic interventions. Further research is needed to investigate the efficacy of pimavanserin and explore other treatment options for individuals with both bipolar disorder and Parkinson's disease.