Depression in narcolepsy – A comparative analysis of depression severity and daytime sleepiness in patients with narcolepsy and idiopathic hypersomnia

Depression and depressive symptoms are consistently reported as a problem for patients with daytime sleepiness in various studies. The present dissertation attempts to compare depression severity and daytime sleepiness in patients with narcolepsy and Idiopathic Hypersomnia. The main objective of this dissertation is to determine whether the depressive symptoms of narcoleptic patients are different from the depressive symptoms of depressed non-narcoleptics. Given the large discrepancy in previous results on this topic, this hypothesis was to be tested in steps, therefore this dissertation is divided into three studies. The first study assesses depressive symptoms in 86 narcoleptic patients with (NC+) and without (NC-) cataplexy (46 women, 40 men), idiopathic hypersomnia (IH) patients (three women, 12 men) and age- and sex- matched healthy controls. Seventy patients were under treatment with stimulants and/or anticataplectics. The second study compares depressive symptoms between 36 narcoleptics (26 women, 10 men) and 34 outpatients with mild to moderate depression (22 women, 12 men). The group of narcoleptics was selected from the sample of patients of the first study (n = 86) who had ≥10 points in the Beck Depression Inventory (BDI). All subjects completed the Beck Depression Inventory (BDI), the Zung Self-Rating Depression Scale (SDS), the Global Impression of Severity of Depression (GSD), the Profile of Mood States (POMS) and Epworth Sleepiness Scale (ESS). The third study identifies the components of depressive symptoms of narcoleptic patients using BDI. The total number of patients had to be increased to meet the basic requirements of a factor analysis. The sample was made up of 114 Caucasian narcoleptic patients (62 women, 52 men). The results show that patients with narcolepsy were more depressed than controls (higher scores in BDI, GSD, SDS, and POMS [in the total score and in all sub scale scores]); however, between the NC+ and NC- patient groups, no differences were found. Women and the patients using antidepressants and stimulants (combination) have a higher probability for depressive symptoms independent of the presence of cataplexy. The daytime sleepiness measured by the ESS (mean score) for the narcoleptic group was higher than the mean scores for the depressive group (p<.001). In the item analysis, differences between the narcoleptic group and depressive disorder group in BDI were found regarding anhedonia. Narcoleptic patients were more likely to continue to feel pleasure compared to patients with depression. Further differences were found in the items loss of appetite and health worries. In SDS, narcoleptics were less impaired in diurnal variation, loss of libido, appetite and weight than patients with depression. Narcoleptics and depressives were more impaired in POMS (total and all sub scales) compared to controls. The factor analysis of BDI revealed that the negative attitude towards self was the component that explained most of the symptoms of depression. Even though this is a component also found in patients with depression without narcolepsy, it is interesting because in patients with narcolepsy it is more manifest than in depressives without this sleep disorder. Taken together, the findings support the assumption that the major psychosocial burden in narcolepsy is associated with sleepiness and not with cataplexy. Female sex and the intake of antidepressants and stimulants together are two determinants connected with depressive symptoms in patients with narcolepsy. The prevention of depressive symptoms should have special focus in women with narcolepsy independent of the presence of cataplexy. Furthermore, with regards to prevention, the focal point should be the negative attitude toward self as the most relevant component. Future studies should concentrate on the impact of medication on depression in patients with narcolepsy