Delusional Disorder Leading to Precipitous Weight Loss: Page 2 of 2

December 14, 2012

Pathophysiology of Delusions in PD 

Understanding the pathophysiology of delusions in PD is challenging, as there is a complex interplay between extrinsic and disease-related factors. It is now known that delusions can result from the PD itself or be an adverse effect of medications, particularly anti-PD agents.2,5 Although dopamine receptor agonists have been most commonly implicated as a source of medication-induced delusions,3 other anti-PD agents, including levodopa, amantadine, and anticholinergics, have also been reported to cause delusions and other psychotic behaviors.2 It is unclear how dopaminergic medications lead to delusions in PD, but because reductions in or discontinuation of these medications have been documented to be at least partly beneficial in remediating the delusions, these agents are thought to play a role in the development of this form of psychosis.3,5 It has been postulated that schizophreniform disorders, affective disorders, Alzheimer’s disease, and PD have a “final common pathway” involving dopamine, and high presynaptic dopamine synthesis capacity in the ascending midbrain system has been associated with the severity of psychotic symptoms.10 However, other neurotransmitter abnormalities are also thought to contribute to psychosis, including y-aminobutyric acid, glutamate, and endocannabinoids, but their role in patients with PD is unclear.10 

Another factor that confounds our understanding of the pathophysiology of delusions in PD is that patients can experience delusions despite receiving antipsychotics.2 Then there are countless other nonpharmacological variables that may be contributing factors, including cognitive impairment, advancing age, duration of the PD, and the presence of major depressive disorder and sleep disturbances.2 These disorders, in combination with the aforementioned factors, contribute to the lack of agreement and clarity regarding the etiology of psychosis in patients with PD, particularly with regard to delusions. In addition, while much is known about brain abnormalities and cognitive deficits that lead to delusions in persons with schizophrenia and other psychological conditions, this information does little to further our understanding about the pathophysiology of delusions in patients with PD.10


Managing delusions in patients with PD requires a multifactorial approach, as there are many considerations. First, it is important to ascertain whether the delusions represent an advancement of PD or whether they have been precipitated by the use of anti-PD medications.4 Second, stressful psychosocial factors (eg, relocation to a new living environment, death of a spouse or grown child, reduced financial security) should be taken into consideration, as such factors have been speculated to contribute to the onset and maintenance of delusional beliefs.2 Finally, with regard to the LTC patient, the psychosocial environment of the facility should be considered, as this can also influence how neuropsychiatric symptoms manifest.8 

LTC staff should understand that delusions are both distressing and debilitating to patients due to the emotional experiences that this particular form of psychosis provides. During their small qualitative study of delusions in eight patients with PD, Todd and colleagues2 identified the following four emotional themes when they conducted a phenomenological analysis of their patients’ accounts: fear (“I got very frightened.”); uncertainty and losing control (“Why is this happening?”); loss of identify and sense of self (“I feel like I’m disintegrating.”); and acceptance (“I’ve just tried to make the best of things.”). Our case patient may be conceptualized as experiencing two of these themes: losing control (ie, feeling that she could not prevent herself from passing gas) and fear (ie, feeling that she would be publically humiliated for inadvertently doing so). 

Since delusions are thought to be part of a disease process or an adverse event of its treatment, the prevailing view of managing psychotic symptoms in PD is largely based on the medical model. Reduction or discontinuation of dopamine receptor agonists (levodopa), amantadine, and anticholinergics is thought to be one approach.1,4 There is some concern, however, with discontinuing dopamine receptor agonists because motoric symptoms will inevitably recur.4 Clinicians are recommended to consider reducing the use of anti-PD drugs in the presence of psychotic symptoms, but they also need to weigh the risks and benefits of doing so and individualize treatment to care for patients with PD as their illness progresses.1 

Because options for treating psychosis in PD patients are limited, antipsychotics can be used despite their limited efficacy in ameliorating symptoms and their inherent safety risks, which include stroke and all-cause mortality.13 Clinicians should keep in mind that safety risks with these agents are increased among elders who also have dementia.13 When prescribing an antipsychotic, the atypical neuroleptic agents quetiapine and clozapine are recommended, as they are least likely to worsen motoric symptoms in PD patients. Although the atypical neuroleptics risperidone and olanzapine can ameliorate psychosis, they have been shown to worsen motoric symptoms, making them less attractive therapeutic options.4 Also, cholinesterase inhibitors (ie, donepezil, rivastigmine) have shown efficacy in attenuating psychotic symptoms in PD, yet without reducing the benefit of dopaminergic treatment for the bothersome motoric symptoms of the illness.4 Before prescribing any antipsychotics to PD patients, nonpharmacological approaches should be attempted to minimize safety risks in this vulnerable patient population. For example, some research has shown that increased socialization can ameliorate visual hallucinations in patients with PD.2,14 Whether psychosocial interventions, such as day programs, therapeutic outings, or other community activities, would be effective in also attenuating delusions remains unclear. 


Neuropsychiatric symptoms are frequently encountered in patients with PD. Visual hallucinations are the most common symptom, but delusions can also occur. Dysregulation of dopamine is thought to play a role in the manifestation of delusions, but it is not known whether the delusions are a component of the PD, precipitated by the initiation of anti-PD medications, or both. Delusions experienced by patients with PD typically encompass paranoia or persecution, but it is not known how or why specific themes manifest. We speculate that the emergence of the case patient’s delusion was the result of many factors, including her PD diagnosis (PD is known to have neuropsychiatric symptoms), initiation of anti-Parkinson medications (these are known to contribute to psychosis), and the presence of several psychosocial stressors (these are known to be contributing factors), most notably her recent PD diagnosis and the loss of her independence after having to relocate to an LTC facility. The underlying theme of these experiences points to loss of control over her body, due to her PD, and over her immediate environment, due to being forced to relocate to an LTC facility. Not being able to control her meals at the facility might have led her to develop a monothematic delusion about food. After various interventions failed to resolve her delusion, a low-dose, atypical antipsychotic was initiated. Although antipsychotics are associated with many safety risks, particularly in elders, when used cautiously and patients are carefully monitored, they can represent an important therapeutic intervention when all other interventions have failed. Use of an antipsychotic resolved our patient’s delusion, and she continues to take this agent under close supervision. Since the agent was initiated, we have observed no abnormal involuntary movements, her weight has remained steady, and she now participates in various activities at the facility. She even recently astounded her family by attending a holiday dinner, and prior to this, she had not left the LTC facility in more than 2 years.


  1. Aggarwal L, Cervo FA. Therapeutic management of late-stage Parkinson’s disease: review of the Movement Disorder Society’s guidelines. Annals of Long-Term Care: Clinical Care and Aging. 2011;19(12):42-46.
  2. Todd D, Simpson J, Murray C. An interpretive phenomenological analysis of delusions in people with Parkinson’s disease. Disabil Rehabil. 2010;32(15):1291-1299.
  3. Roane DM, Jean D. Pharmacologic options for managing psychosis in Parkinson’s disease. Annals of Long-Term Care: Clinical Care and Aging. 2005;13(5):42-45.
  4. Stefanis N, Bozi M, Christodoulou C, et al. Isolated delusional syndrome in Parkinson’s disease. Parkinsonism Relat Disord. 2010;16(8):550-552.
  5. National Parkinson’s Foundation. What are the symptoms of psychosis? Accessed November 19, 2012.
  6. Zuidema S, Koopmans R, Verhey F. Prevalence and predictors of neuropsychiatry symptoms in cognitively impaired nursing home patients. J Geriatr Psychiatry Neurol. 2007;20(1):41-49.
  7. Coltheart M, Langdon R, McKay R. Delusional belief. Annu Rev Psychol. 2011;62:271-298.
  8. Murray GK. The emerging biology of delusions. Psychol Med. 2011;41(1):7-13.
  9. Goldstein R. Incompleteness: The Proof and Paradox of Kurt Godel. New York, NY: WW Norton & Co, 2005.
  10. Wikipedia. Martha Mitchell effect. Accessed November 29, 2012.
  11. Karim S, Byrne EJ. Treatment of psychosis in elderly people. Advances in Psychiatric Treatment. 2005;11(4):286-296.
  12. Zahodne LB, Fernandez HH. Pathophysiology and treatment of psychosis in Parkinson’s disease: a review. Drugs Aging. 2008;25(8):665-682.
  13. Williams-Gray CH, Foltynie T, Lewis SJ, Barker RA. Cognitive deficits and psychosis in Parkinson’s disease: a review of pathophysiology and therapeutic options. CNS Drugs. 2006;20(6):477-505.
  14. Roever CP, Vyas BB, Barnett MC, Sheyner I, Stewart JT. Visual hallucinations in long-term care. Annals of Long-Term Care: Clinical Care and Aging. 2012;20(2):25-30.


    The authors report no relevant financial relationships.


    Address correspondence to:

    Julie Pullen, GNP, NP-C

    St. Vincent’s Long-Term Care Services

    1101 North 27th Street, Suite 101

    Billings, MT 59101