Visual Hallucinations and Psychosis in Parkinson's Disease

Visual hallucinations in Parkinson’s disease represent one of the most distressing non-motor complications, characterised by the perception of images—people, animals or objects—in the absence of corresponding external stimuli. They typically emerge in the mid to late stages of disease, affecting up to 50 percent of patients over time, and often herald more severe cognitive decline and increased care needs. Psychosis in this context extends beyond simple visual phenomena to include illusions, passage and presence hallucinations, and in some cases fixed delusional beliefs. The underlying mechanisms are multifactorial, involving a complex interplay between disrupted cortical networks, impaired thalamic filtering and imbalances in neurotransmitter systems. Aberrant activity in large-scale brain networks—principally the default mode network, dorsal and ventral attention systems—and altered thalamocortical rhythmicity undermine normal sensory integration and reality monitoring. Reduced cholinergic and GABAergic transmission in visual and associative cortices compounds these changes. Clinically, the onset of visual hallucinations demands careful review of dopaminergic and adjunctive therapies, optimisation of sensory input and consideration of antipsychotic or cholinesterase-inhibiting agents. Early recognition and a multidisciplinary management strategy are essential to maintain quality of life, mitigate caregiver burden and delay progression to dementia.

Research from Nature Portfolio

No recent Nature Portfolio content available.

Visual Hallucinations and Psychosis in Parkinson's Disease publication trend

The graph below shows the total number of articles in visual hallucinations and psychosis in parkinson's disease across all publications each year (not limited to Nature Index journals).

Technical terms

Visual hallucination: A perceptual experience of seeing objects or scenes when no corresponding external stimulus exists.

Psychosis: A clinical syndrome involving impaired reality testing, including hallucinations and delusional beliefs.

Default Mode Network (DMN): A set of interconnected brain regions active during rest and self-referential thought, whose abnormal persistence during tasks is linked to hallucinatory experiences.

Thalamocortical Dysrhythmia: A state of altered rhythmic activity between thalamic nuclei and the cortex that disrupts normal sensory gating and network balance, precipitating psychotic symptoms.

GABAergic transmission: Inhibitory signalling mediated by γ-aminobutyric acid in the brain; reductions in GABAergic tone in visual and associative areas contribute to hyperexcitability and hallucinations.

References

1. Understanding visual hallucinations: A new synthesis. Neuroscience & Biobehavioral Reviews (2023).
2. The central role of the Thalamus in psychosis, lessons from neurodegenerative diseases and psychedelics. Translational Psychiatry (2023).
3. Visual hallucinations in neurological and ophthalmological disease: pathophysiology and management. Journal of Neurology Neurosurgery & Psychiatry (2020).
4. A questionnaire-based (UM-PDHQ) study of hallucinations in Parkinson's disease. BMC Neurology (2008).
5. Auditory and visual hallucination prevalence in Parkinson's disease and dementia with Lewy bodies: a systematic review and meta-analysis. Psychological Medicine (2018).
6. On visual hallucinations and cortical networks: a trans-diagnostic review. Journal of Neurology (2015).