In the twilight zone: An epidemiological study of sleep-related hallucinations

Area of Science:

• Neuroscience
• Psychiatry
• Epidemiology

Background:

• Few studies investigate hypnagogic/hypnopompic hallucinations (HHHs), sleep-onset/offset experiences.
• HHH prevalence may exceed that of daytime hallucinations.
• Research exploring HHHs' characteristics and comparison to daytime hallucinations is limited.

Purpose of the Study:

• To determine the prevalence of HHHs in various modalities within the general population.
• To investigate phenomenological differences between sleep-related (HHHs) and daytime hallucinations.
• To test hypotheses regarding mental health and wellbeing in individuals with HHHs versus daytime hallucinations.

Main Methods:

• Utilized data from a cross-sectional epidemiological study (n=2533) in the Norwegian general population.
• Categorized participants into groups: controls, only HHHs, only daytime hallucinations, and both.
• Compared groups using ANOVA and chi-square tests for prevalence and phenomenological differences.

Main Results:

• Auditory HHHs prevalence: 6.8%; multimodal HHHs: 12.3%; out-of-body experiences: 32.2%.
• Individuals with only auditory HHHs reported significantly lower mental health burden, less frequent/disturbing hallucinations, and later age of onset compared to those with daytime hallucinations.
• Purely auditory HHHs had a significantly later age of first onset (28.2 years) than purely daytime (20.9 years) and combined groups (19.1 years).

Conclusions:

• Sleep-related hallucinations are common, often co-occurring with daytime hallucinations.
• A distinct subgroup experiencing only HHHs (2.4%) shows health-related factors closer to non-hallucinating individuals.
• Further research on HHHs is warranted, with potential avenues for future studies suggested.