Positive psychology and sleep: the influence of an internet-based exercise

Associations between psychopathology and poor sleep have been well established by previous research. This has been motivated by the drive to uncover and undo pathology.
An alternative approach offered by positive psychology considers whether those who have good sleep quality (SQ) show high levels of subjective well-being (SWB). Evidence is
limited, but recent findings have linked good sleep with constructs that are central to SWB, including trait gratitude; how orientated people are to the positive things around them.

Aims:
The main aim of this thesis is to examine the effect of a gratitude intervention on SQ. A secondary aim is to explore the relationships between SQ, SWB and pre-sleep cognitions.

Design:
A total of 300 participants took part in the cross-sectional study. These were classified as having high (n = 138) and low SQ (n = 162) according to the Sleep Impairment Index (SII). Groups were compared on measures of Satisfaction With Life (SWLS), gratitude (GQ-6) and pre-sleep cognitions (SST:60). Hypotheses were guided by
the one piece of research that has previously explored these constructs. Individuals with low SQ were then invited to participate in a novel intervention study (N = 51). Participants were randomized into a self-guided Three Good Things in Life gratitude intervention (n = 25) or events listing control intervention condition (n = 26) that ran across 7 days. Repeated measures analysis of variance was used to assess change in SQ and pre-sleep cognitions between baseline and follow-up. Hierarchical linear modelling (HLM) was used to explore daily measurements of sleep and affect.

Results:
Results supported previous work in finding positive relationships between high SQ and measures of SWB, including
trait gratitude. Those completing the gratitude intervention reported significantly improved SQ according to the Pittsburgh Sleep Quality Index (PSQI), compared to the control condition. A higher proportion of participants in the gratitude intervention fell on or below the clinical threshold of >5 on the PSQI after the intervention (n = 11), compared to those in the control intervention condition (n = 3). The effect of intervention on presleep
cognitions between baseline and follow-up was approaching significance. No significant mediational influences were found using HLM. Conclusions: This research demonstrates the relationship between SWB and gratitude in relation to SQ and the outcome of the intervention suggests that it could be employed to improve public health in relation to sleep.