Parkinson’s disease (PD) is widely associated with its characteristic motor symptoms including tremor, rigidity, and bradykinesia (slow movement). 1 Though these symptoms are undoubtedly an essential aspect of PD and greatly impact the quality of life of PD patients, the neuropsychiatric symptoms of PD are less acknowledged. With the increasing societal importance of mental health awareness, a better understanding of the neuropsychiatric disorders is also relevant. Neuropsychiatric symptoms are the manifestations of neurological disorders such as PD on mental health, including one’s behaviour and mood. 2 The most common and debilitating neuropsychiatric symptoms caused by the neurodegeneration characteristic of PD are depression, anxiety, apathy and psychosis.3
Clinical depressive symptoms are prevalent in approximately 30 to 35% of PD patients. 3 These include lingering feelings of sadness and depressed moods, worthlessness and guilt.3 Bradykinesia, weight loss and sleep difficulties also arise, however are also common motor symptoms of PD and thus make diagnosis of depression more difficult. Thus, the reported prevalence of depression in PD patients is likely lower than reality.
Anxiety disorders are prevalent in 25 to 43% of PD patients.3 Generalized anxiety disorder is the most prevalent, with agoraphobia, social phobia and panic disorder being less so prevalent. In addition, not otherwise specified anxiety disorders also manifest from PD specific situations, such as anxiety about falling, potential of developing “embarrassing symptoms” and treatment plans.3 Though also hard to diagnose, current studies suggest this anxiety occurs in approximately 13.3% of PD patients.3 These anxiety disorders exacerbate existing PD motor symptoms as patients experience restlessness, excessive concern, and tension.
Apathy refers to a loss of interest and participation in daily life, as well as an overall feeling of indifference. Apathy is prevalent in 39.8% of PD patients and is more common in the older PD affected population, as well as those with more severe presentation of PD symptoms. 3 Apathy worsens a PD patient’s already difficult ability to take care of themselves and thus further burdens caregivers as well as the patient.
Finally, psychosis may ensue in PD patients causing hallucinations, illusions, and delusions. The most common of these include passage and presence hallucinations and/or illusions, in which an individual perceives something is passing their visual field and that someone is present in their surroundings, respectively.3 These episodes are highly prevalent, present in among approximately 50% of PD patients.3 Further, severity and frequency of psychotic episodes including the aforementioned symptoms tend to progress over time with PD.
The significance of neuropsychiatric symptoms in PD cannot be ignored. The range of different symptoms add to the debilitating condition of PD while being one of the most poorly known and understood factors of the disease. Further research is required to understand how these symptoms result from the neurodegeneration involved in PD. Though the need for more research may seem disheartening, there is no better time in the current state of the world in which mental health is becoming more and more relevant and destigmatized. A further understanding of the mechanisms and treatments of neuropsychiatric symptoms of PD may provide both patients and their caretakers with some peace of mind amidst this very emotionally heavy category of symptoms.
1. Parkinson's UK. Motor symptoms of Parkinson’s. Parkinsons.org.uk. Published 2020. https://www.parkinsons.org.uk/information-and-support/motor-symptoms-parkinsons
2. American University of Antigua. What is Neuropsychiatry? American University of Antigua. Published May 13, 2022. https://www.auamed.org/india-blog/what-is-neuropsychiatry/
3.Dujardin K, Sgambato V. Neuropsychiatric Disorders in Parkinson’s Disease: What Do We Know About the Role of Dopaminergic and Non-dopaminergic Systems? Frontiers in Neuroscience. 2020;14. doi:https://doi.org/10.3389/fnins.2020.00025