Abstract
Background
Although previous studies reported a link between sleep dysfunction and psychotic symptoms, more detailed information is needed to translate this association into clinical practice. This study investigates the impact of different aspects of sleep quality on prevalence, type and severity of psychotic-like experiences, in a large general population sample. In doing so, we distinguish between hallucinations in the auditory (AH) and visual (VH) domains and delusions, to arrive at a more comprehensive understanding of the detrimental effects of impaired sleep.
Methods
An online survey was used to gather information on self-reported psychotic-like experiences and sleep quality in a sample of 10.301 Dutch participants (median age 32 yrs; 68.9% females). The Questionnaire for Psychotic Experiences (QPE) was used to assess aspects of AH and VH. A subset of the participants also filled-out a second part of the QPE regarding occurrence of delusion. Furthermore, a measure of general sleep quality was derived based on seven sleep domains as assessed using the Pittsburgh Sleep Quality Index (PSQI).
Binomial logistic regression was used to investigate the effects of the seven sleep domains on the likelihood that participants had experienced hallucinations in the preceding week, using 3324 participants with and a random subsample of 3391 participants without such experiences. The same analysis was performed on the data regarding delusions, using 438 participants with and a random subsample of 445 participants without delusions in the past week. Reported odds ratios (OR) reflect the increment in likelihood of occurrence of hallucinations and delusions.
To further assess whether impaired sleep affects the level of distress caused by hallucinations, participants were divided into ‘good’ and ‘poor’ sleepers using a cut-off score of 5 points on the total PSQI score. Chi-square tests were then used to compare the two groups on occurrence of distressing vs non-distressing AH and VH.
Results
Impaired sleep showed to entail significant predictors of the prevalence of hallucinations. Specifically, sleeping less than 5 hours a night (OR 1.88), having sleep disturbances more than 3 times a week (OR 5.81), the use of sleep medication more than 2 times a week (OR 1.61) and decreased daytime functioning more than 3 times a week (OR 1.87) increased the odds to experience hallucinations, as compared to participants without these sleep difficulties. Furthermore, experiencing sleep disturbances more than 2 times a week (OR 9.24) and decreased daytime functioning more than 2 times a week (OR 5.53) also strongly increased the odds to experience delusions. Subjective sleep quality, sleep latency, and sleep efficiency were not significant predictors for the prevalence of hallucinations or delusions.
Importantly, sleep impairment also affected the experienced distress as caused by hallucinations. A larger proportion of the poor sleepers than of the good sleepers experienced distressing AH (p < .001) and reported that the AH had a negative impact on their functioning (p < .001). Likewise, a larger proportion of the poor sleepers than of the good sleepers reported distressing VH (p < .001) and reported a negative impact of VH on their functioning (p < .001).
Discussion
Sleep impairments were associated with increased prevalence of psychotic-like experiences, and with more severe distress as caused by hallucinations. Sleep restoration should be explored as a first line intervention for people suffering from psychotic-like experiences. In case of delusions, such interventions should be directed at decreasing the number of nightly disturbances, while for individuals suffering from hallucinations additional focus should be put on increasing the achieved hours of sleep.
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