Purpose
The aim of the systematic review and meta-analysis was to determine the magnitude and
strength of the loneliness-psychosis relationship, and to synthesise current evidence. The aim
of the empirical investigation was to establish whether, in older people, loneliness may increase
proneness to auditory hallucinations and perceiving visual human-like features in ambiguous
stimuli.
Methods
For the meta-analysis a search of electronic databases was conducted (PsychINFO, MEDLINE,
EMBASE and Web of Science). Studies were included if they reported usable data relating to
the association between loneliness and psychotic symptoms. A random effects meta-analysis
was used to compute a pooled estimate of the correlation, together with 95% Confidence
Intervals (CI). Study quality and outcome quality were systematically assessed using adapted
versions of the Agency for Healthcare Research and Quality (AHRQ) tool and GRADE
approach, respectively. For the empirical study, a parallel group experimental design with
random allocation to experimental conditions was employed. Participants (62 healthy adults
aged 65 and above) were assigned to one of the two conditions – the experimental condition or
a control condition. A loneliness induction procedure was employed in the experimental
condition whereas participants in the control condition completed a neutral task. A logistic
regression was conducted to evaluate performance on auditory and visual tasks across the
groups and an odds ratio was calculated.
Results
Thirteen studies were included in the meta-analysis, providing data from 15,647 participants.
A moderate association between psychosis and loneliness was observed (k=13, N=15,647,
r=0.32, 95% CI 0.20, 0.44; I2 97.56%; moderate quality evidence). Whether loneliness was
assessed by single-item or a more comprehensive measure had no moderating effect on the
estimate.
The experimental study revealed that participants in the neutral condition were significantly
less likely to hear words in ambiguous stimuli than those in the experimental condition (OR =
0.70, 95% CI 0.51 – 0.94, p < 0.05). Exploratory analysis revealed that higher scores on the
state loneliness measure were associated with an increase in the likelihood of hearing words
(OR=1.17, 95% CI 1.01-1.35, p = 0.03). No effect of loneliness induction was found on
perceiving human-like features in ambiguous visual stimuli.
Conclusions
The meta-analysis confirmed a significant positive relationship between loneliness and
psychosis, while the experimental study suggested that loneliness may have a causal role in the
development of subclinical auditory experiences in older people. Further studies examining
whether loneliness is involved in proneness to other psychotic experiences would be beneficial