Parkinson's disease: mental and behavioural disorders

In addition to motor dysfunctions, which are well known symptoms of Parkinson's disease, mental, behavioural, psychotic and cognitive disorders may also occur.

What mental disorders can be caused by Parkinson's disease? 

Anxiety, depression, hyperemotionality, stress and apathy (lack of motivation and/or desire) are the most common mental disorders in Parkinson's disease. They may appear at the same time as motor disorders or can occur later.

Depression 

The number of individuals suffering from depression is much higher than average among Parkinson's disease patients. This can be explained by the difficulties linked to the symptoms, the impact of the condition on the relationships with other people, and by the apprehension of the way the disease may progress in the future.

However, it is important to distinguish between depression as a symptom of Parkinson's disease and depression caused by the announcement of the diagnosis or the fear of the disease progression.

In fact, depression is often present before the development of motor impairment, because dopamine plays an important role in mood regulation. Depression can therefore be a symptom that can help reveal Parkinson's disease before other symptoms set in.

Anxiety 

Almost half of all Parkinson's patients suffer from anxiety. It is thought to be linked to the deterioration of the serotonin production system located in the brain.

Hyperemotionality and stress 

Parkinson's disease amplifies emotions and increases the level of stress, which in turn intensifies certain motor symptoms such as tremors or blockages. Emotions such as joy, sadness or anger can overwhelm patients. This increased sensitivity is usually due to the disease but can also be linked to side effects from medication.

Apathy 

Apathy and depression can be difficult to distinguish since they are often concomitant, with common symptoms such as loss of interest, psychomotor slowing, loss of energy, significant fatigue, etc. However, apathy is different from depression because there is no sadness. It is defined by its own psychological disorders such as lack of initiative, decrease in emotional responses and indifference.

What behavioural disorders can be caused by Parkinson's disease? 

Behavioural disorders in Parkinson's disease may include impulse control disorders, psychosis or dopamine dysregulation syndrome.

Impulse control disorders 

According to the DSM-IV, these disorders are characterised by the inability to resist an impulse or behaviour that significantly impairs the patient's family, social or professional life.

For patients with Parkinson's disease, these impulse control disorders may manifest themselves as:

• Addiction to gambling,
  
• Compulsive shopping,
  
• Hypersexuality,
  
• Nocturnal hyperactivity,
  
• Risk-taking behaviour,
  
• Eating disorders,
  
• Development of creativity.
  

These disorders are directly related to the antiparkinsonian drugs, the dopamine agonists.

Psychosis 

In Parkinson's disease patients, psychosis takes the form of hallucinations, which are most often visual, as well as delusions, a feeling of being prosecuted, agitation or confusion.

Parkinson's disease psychosis is also related to dopamine agonists. In some cases, it may be provoked by the disease itself, but only if accompanied by cognitive disorders, which occur much later in the course of the disease.

Dopamine dysregulation syndrome 

Dopamine dysregulation syndrome induces physical, social and emotional dysfunction. Its prevalence is estimated at 13.7% in patients on dopamine agonists.

The syndrome manifests itself by stereotyped behaviour, irritability, hypomania, paranoid or delusional ideas and intolerance to frustration.

What cognitive disorders may be caused by Parkinson's disease? 

The nature of the cognitive problems, the time of their onset and their evolution differ significantly from one Parkinson's patient to another.

The executive functions are often the first ones to be affected. This means that patients start experiencing difficulties in paying attention, planning complex activities, finding alternatives when faced with an impasse, as well as difficulties in maintaining and manipulating information in memory.

In addition, learning abilities are also impaired: the acquisition of new information and its retrieval become more difficult.

Nevertheless, the ability to retain new memories is preserved, especially in the early stages of the disease.

Mild cognitive impairment

This concept defines cognitive functioning that is below average for an individual's age and education.

Mild cognitive impairment affects about 1/3 of patients with Parkinson's disease. The evolution of mild cognitive impairment is variable (return to normal cognitive functioning, stabilisation or deterioration). It is nevertheless a major risk factor for the development of dementia.

Dementia 

Dementia is diagnosed when the patient's social or occupational activities become difficult to perform due to significant cognitive decline. The identification of risk factors for dementia in Parkinson's disease is therefore crucial for early diagnosis and thus for the development of preventive therapeutic approaches.

Here are some risk factors:

• Age,
  
• The presence of a mild cognitive disorder,
  
• The presence of restless dreams,
  
• Certain psychotic symptoms such as hallucinations,
  
• Or the more rigid form of the disease (without tremors).
  
  

The management of psycho-behavioural disorders in Parkinson's disease differs according to the type of these disorders.

Thus, the patient's antiparkinsonian treatment, which may be the cause of certain disorders, can be altered, if necessary, by decreasing, increasing or modifying the molecules.

Psychiatric (drug and/or non-drug) or psychological support may also be offered to patients with Parkinson's disease.