Subjective sleep dissatisfaction in depression
Although the relationship between sleep and depression has been examined extensively, much of this has focused on objective measures, such as sleep electroencephalography, whereas subjective measures have been studied in less detail. A key focus of this thesis is the subjective perception of sleep in depression. The research questions asks whether sleep dissatisfaction in depressed participants is related to their mood, regardless of sleep timing perceptions; while sleep dissatisfaction in those without depression is more likely to be related to poor sleep timing perceptions, irrespective of mood. The initial chapters focus on 'sleep architecture'; the relationship between sleep disorders and depression; methods used to measure objective and subjective sleep; and include an overview of the observed effect of antidepressants on sleep. As it has been argued that poor sleep satisfaction in depression may be maintained by negative cognitive bias, the main prediction was that perceived sleep satsifaction, but not perceived sleep timing, would be related to perceived quality of life and mood for those with current depressive symptoms; while for those without such symptoms, perceived quality of life and mood would more likely be related to perceived sleep timing. Three original studies explored these predictions: the first indicated that, in depressed patients, sleep satisfaction perceptions (SSP; 3 out of 5 items significantly different; p<.05), and not sleep timing perceptions (STP; 2/8), were more likely to be related to perceived quality of life (QoL), while the opposite was found with the healthy controls (SSP 2/5 vs. STP 4/8). The second study replicated this finding (depressed: SSP 3/5, STP 0/11; vs. not depressed: SSP 1/5, STP 9/11; p<.05). The third original study found fewer between-group differences (mostly due to abnormally porr QoL scores in the student group), but regression analysis indicated that STP variance was related to the absence of depression, and the presence of anxiety (anxiety: 3/6 STP variables, p<.01; depression: 0/6); while SSP variance was related to the presence of depression, but not anxiety or the absence of depression (depression: 2/4 SSP variables, p<0.001; no depression: 0/4; anxiety: 0/4). In each of these studies the main hypothesis was supported. The final chapter concludes by considering the study findings and critically examining the methods; possible implications for futher research and clinical practice are explored.