Influence of State Anxiety on the Relationship Between Sleep Disturbances and Depressive Symptomology
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Influence of state anxiety on the relationship between sleep disturbances and depressive symptomology
Submitted as PSY3032 Lab Report
Tutor: Minn Chan
Word Count: 1812
This study aimed to establish whether an independent relationship exists between depressive symptomology and sleep disturbances and build on current knowledge by determining the extent to which state anxiety influences this relationship. It was expected that there would be a significant relationship between sleep disturbance and depression and that this would remain even when anxiety was controlled for. 321 Monash University undergraduate psychology students (Mage = 24.18, SDage = 7.70) were asked to voluntarily complete two online questionnaires. The first, the Pittsburg Sleep Quality Index was used to measure sleep quality while the DASS-21 was used to measure depression, anxiety and stress. There was a significant relationship between depressive symptomology and sleep disturbances and this remained even after state anxiety was controlled for. Therefore it was concluded that there is a significant relationship between sleep disturbances and depression independent of any influence of state anxiety.
Sleep quality is a fundamental factor in cognitive functioning and mood regulation as well as in general mental health and well-being. Sleep disturbances and insomnia is becoming increasingly prominent affecting approximately 30% of adults (Ohayon, 2002). Depressive symptoms and disorders are often supplemented by poor quality sleep. Indeed, depressed subjects frequently suffer from disturbed sleep, with an abnormal amount of rapid-eye-movement (REM) sleep. Sleep impairment has been discussed as a prodromal symptom of depression; with some sleep abnormalities identified as specific markers for major depressive disorder (MDD), such as abnormal REM sleep (Nutt, Wilson & Paterson, 2008). Equally, people suffering from insomnia or other sleep disturbances appear to be at a higher risk of developing MDD and having longer and more chronic depressive episodes (Tsuno, Besset and Ritchie, 2005). Tsuno, Besset and Ritchie (2005) estimated that up to 90% of people diagnosed with depression also complained of poor sleep.
As well as the co-occurrence with sleep disturbances, depression has been shown to have a high co-morbidity with anxiety. It has been estimated that approximately 60% of people diagnosed with depression also meet the criteria for clinical anxiety disorder (Kaufman & Charney. 2000). In one study, Atalay (2011) demonstrated that 40-60% of clinical patients suffering from insomnia also carried symptoms associated with MDD and anxiety disorders. However, the results yielded found that there was no significant correlation between depression and insomnia but rather showed that state anxiety was most associated with insomnia. Therefore Atalay (2011) concluded that sleep difficulties may be the result of interactions between insomnia and state anxiety, not depression.
Alternatively, Johnson, Roth and Breslau (2006) conducted a directional study between insomnia, anxiety and depression in adolescents to understand potential etiological connections. Proportional Hazards models were used to show that any prior anxiety disorder was associated with increased risk of insomnia (HR= 3.5) and that prior insomnia was associated with the onset of depression (HR=3.8). This suggests that although the etiological associations remain unclear, there is a definite relationship between insomnia and both anxiety and depression independent of each other.
To build on this previous research, it is important to confirm the association between sleep disturbance and depression in non-clinical populations and look at the confounding effects of state anxiety on this relationship. This study aimed to establish the extent to which state anxiety influences the relationship between sleep disturbances and depressive symptomology. It was expected that there would be a significant positive relationship between depressive symptomology and sleep disturbance in non-clinical populations. It was further hypothesized that this relationship would remain significant after state anxiety was controlled for.
Participants were made up of 321 Monash University 3rd year undergraduate psychology students ranging from ages 19-60 years, consisting of 251 females and 70 males (Mage = 24.18, SDage = 7.70). Students were asked to voluntarily participate in online self-report questionnaires consisting of a shortened version of the Depression, Anxiety and Stress Scale (DASS-21) and the Pittsburgh Sleep Quality Index (PSQI).
The DASS-21 (Lovibond & Lovibond, 1995) is a set of three self-report scales designed to measure the severity of the defining symptoms of depression, anxiety and stress. In the clinical setting the DASS-21 is primarily used to determine the root of emotional disturbance as part of the broader aspect of clinical assessment. The DASS-21 can be used to measure current state or change over time in symptoms of depression, anxiety and stress. Each of the three DASS scales contains seven items assessed through a 4-point scale so that greater scores correlate with greater symptomology. Cronbachs alphas for the DASS–21 subscales were .94 for Depression, .87 for Anxiety, and .91 for Stress showing high internal consistency (Yusoff, 2013).
The PSQI (Buysse, Reynolds, Monnk, Berman & Kupfer, 1989) is an assessment tool measuring seven aspects of sleep: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleep medication, and daytime dysfunction over the last month to determine severity of sleep disturbance (Smyth, 2007). The PSQI consists of four unrestricted questions and nineteen questions using a Likert Scale from 0-3 in increasing negative impact. A total sum of 5 or more indicates “poor” quality of sleep. The PSQI has an overall Cronbach’s alpha of .83, indicating a high level of internal consistency (Buysse, Reynolds, Monnk, Berman & Kupfer, 1989).
After receiving ethical approval