Minor Hallucinations Common, Impactful in Parkinson Disease

More than 1 in 3 patients with Parkinson disease were found to experience minor hallucinations, which were linked with worse quality of life and poor sleep outcomes.

Minor hallucinations were found to be the most common psychotic symptom in patients with Parkinson disease (PD), in which those affected reported reduced health-related quality of life (QOL) and greater sleep symptom burden. Findings were published in Behavioural Neurology.

Although PD psychosis affects up to 75% of patients throughout the disease course, researchers highlight that prevalence of psychotic symptoms, including minor/major hallucinations and delusions, are typically understated and are not fully considered as key characteristics of the condition.

In fact, findings of a recent study showed that just 11% of caregivers reported having been educated by a physician on PD psychosis, with more respondents (21.4%) learning from personal research.

“Minor hallucinations deserve widespread attention because it is the most frequent and earliest type of psychotic phenomenon in PD and occurs even before the onset of motor symptoms,” said the researchers. “Minor hallucinations might also be an early predictor of a severe psychotic and cognitive state.”

Seeking to improve comprehension of the prevalence and clinical factors related to minor hallucinations in patients with PD, they derived demographic information from 262 patients with PD receiving care at the Brain Hospital of Nanjing Medical University between May 2019 and January 2021.

Participants answered a series of clinical assessment questionnaires, with results of the Movement Disorders Society Unified Parkinson’s Disease Rating Scale Part I leveraged to classify patients into eight strata:

  • No hallucination
  • Isolated minor hallucination
  • Isolated major hallucination
  • Isolated delusion
  • The combination of these psychiatric symptoms

Among the study cohort, 102 (38.9%) patients with PD experienced minor hallucinations, including 74 patients with isolated minor hallucinations (28.2%) and 28 patients with combined minor hallucinations (10.7%). Moreover, 14 patients and 1 patients reported incidence of isolated major hallucinations and delusions, respectively, and up to 32 (12.2%) patients had more than one kind of psychiatric symptoms. No hallucinations or delusions were reported by 141 patients.

Of the 74 patients with isolated minor hallucinations, the most common were visual illusion (48.4%), which included object misidentification (19.7%), pareidolias (13.9%), and kineptosia (14.8%).

Compared with patients with PD who reported no hallucinations, those with minor hallucinations were significantly associated with longer disease duration (P = .011), different daily levodopa equivalent dose (P = .038), and higher percentage of levodopa (P = .013) and dopamine-receptor agonist use (P = .042).

After accounting for confounding variables, patients with minor hallucinations were shown to have worse QOL and more severe nonmotor symptoms, including poor sleep quality (P < .001) and rapid eye movement sleep behavior disorder (RBD; P = .001), compared with those who did not have minor hallucinations.

Findings of an additional binary logistic regression model confirmed the associations between incidence of minor hallucinations and RBD, sleep quality, and health-related QOL.

In concluding, the study authors said that future studies on minor hallucinations need to confirm and expand the related clinical factors, which will offer strategies to improve the QOL of patients with PD.


Zhong M, Gu R, Zhu S, et al. Prevalence and risk factors for minor hallucinations in patients with Parkinson’s disease. Behav Neurol. Published online October 4, 2021. doi:10.1155/2021/3469706

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