Cognitive Changes in Parkinson's Disease

By Miriam L. Hirsch, M.S., APDA Information & Referral Center Coordinator, Charlottesville, VA
Carol Manning, PhD, Associate Professor of Clinical Neurology and Co-Director of the Memory Disorders Center University of Virginia Health System, Charlottesville, VA

Parkinson's disease (PD) is a complex condition that has numerous symptoms associated with it. The primary symptoms of PD involve changes in movement. However, a variety of other symptoms can occur as well. Changes in cognition or one's ability to think, reason and remember may develop and there are many factors that can contribute to these changes. The more common cognitive changes in PD will be discussed later, however an accurate assessment is needed in order to establish an appropriate treatment strategy for the patient.


Bradyphrenia, or a slowing of the ability to think, can occur in some patients with PD. Just as it takes more time to rise from a chair, more time may be needed to respond intellectually. It takes longer to process or make sense out of information and this can be frustrating to both patient and care partner. Bradyphrenia may be misinterpreted as intentional behavior, a lack of interest or even stubbornness but it is important to understand that changes in the brain are the cause of the symptom.

To pressure an individual who is having these problems is stressful and will, no doubt, make matters worse. People with PD may also find it difficult to come up with other ways of doing things or to shift from one subject to another. These changes in cognition may be mistaken as intentional, and the individual is labeled as being too rigid and inflexible. A portion of the brain involved in this type of thinking can be affected in some people with PD.


Memory remains relatively unaffected in PD. However, some individuals may experience difficulties remembering where and when particular events occurred without being given some kind of cue. For example, people with PD recall information much better if given multiple choices to select from, and they benefit from using cues more than those of a similar age without PD.


Significant language changes are relatively uncommon in PD, however some subtle changes may occur. For example , speech often becomes slower and spontaneous speech is reduced. People with PD may not initiate conversations as often if at all. These changes can be misinterpreted as indifference and can result in poor communication.


Significant and dramatic changes in memory, reasoning ability, language and attention may develop in a small number of people with PD. As people age, the risk for dementia, the progressive decline in the ability to think, reason and remember, increases. If an individual develops dementia, he/she will need increased care and supervision.


Depression is another possible cause of cognitive changes in those with PD. It is significantly more common in those with PD than in the general population. Twenty five percent of people with PD experience symptoms of depression within one year of the onset of PD symptoms. The development of depressive symptoms is unlikely to be due to difficulty adjusting to the diagnoses alone. Several of the symptoms of PD are similar to the symptoms of depression. For example, loss of interest in activities, fatigue, change in weight and social withdrawal are characteristics of both PD and depression. This similarity in symptoms can result in an underdiagnosis of depression in those with PD. Furthermore, the person with PD may not even recognize that he/she is depressed. On a more positive note, depression is a very treatable illness and can be controlled with a combination of medication and cognitive-behavioral therapies. If left untreated, depression can have serious negative consequences, interfering with cognition and thereby quality of life.

Medication Side Effects

People with PD have quite an array of medications available to control the symptoms of the disease. However, managing the symptoms of PD becomes increasingly more difficult as the illness progresses. The development of side effects and changes in the steady response to medications pose numerous challenges to patient, family and health-care provider. Change in cognitive ability is a potential side effect of every medication used to treat PD. Therefore, people with PD need to know what side effects are associated with the medications they are taking. If cognitive decline is experienced, a healthcare provider should be notified immediately.


In conclusion, some people with PD experience changes in mood and cognitive ability. The most common changes include slowed ability to think and process information. Decreased ability to generate new ways of solving problems may be apparent. While changes in memory are less frequent, some people with PD forget where and when the information was obtained but remember the information itself. Dementia develops in some people with PD and advancing age is a significant risk factor. Depression is a relatively common problem in PD and is underdiagnosed in this population group. Regardless of the type of cognitive changes experienced, accurate assessment is essential if the symptoms are to be treated.

People with PD need to be aware of possible cognitive problems and should report any symptoms to their health care providers.