Depression in narcolepsy– A comparative analysis of depression severity and daytime sleepiness in patients with narcolepsy and idiopathic hypersomnia Inaugural-Dissertation zur Erlangung der Doktorwürde der Philosophischen Fakultät II (Psychologie, Pädagogik und Sportwissenschaft) der Universität Regensburg vorgelegt von Cecilia Jara Opazo aus Santiago de Chile Regensburg 2011 1 Erstgutachter: Prof. Dr. J. Zulley Zweitgutachter: Prof. Dr. K. Lange 2 TABLE OF CONTENTS 1. GENERAL INTRODUCTION....................................................................................6 2. THEORETICAL PART..............................................................................................8 2.1. Definition of excessive daytime sleepiness...................................................8 2.1.1. Evaluation of sleepiness....................................................................8 2.1.2. Causes of excessive daytime sleepiness..........................................9 2.1.3. Hypersomnias of central origin..........................................................9 2.2. Narcolepsy...................................................................................................13 2.2.1. The history of the diagnosis of narcolepsy.......................................13 2.2.2. Classification: narcolepsy with and without cataplexy......................16 2.2.3. Clinical symptoms............................................................................18 2.2.4. Etiology.............................................................................................23 2.2.5. Pathophysiology...............................................................................25 2.2.6. Epidemiology....................................................................................27 2.2.7. Diagnosis..........................................................................................27 2.2.8. Treatment of narcolepsy..................................................................28 2.3. Idiopathic hypersomnia................................................................................33 2.3.1. History of the diagnosis of idiopathic hypersomnia..........................33 2.3.2. Classification: idiopathic hypersomnia with and without long sleep time.........................................................................................35 2.3.3. Clinical symptoms............................................................................37 2.3.4. Etiology............................................................................................38 2.3.5. Pathophysiology...............................................................................38 2.3.6. Epidemiology....................................................................................38 2.3.7. .Diagnosis..........................................................................................39 2.3.8. Treatment of idiopathic hypersomnia...............................................40 2.4. Depression...................................................................................................41 2.4.1. Historical aspects of depression......................................................41 2.4.2. Classification and different names for depression...........................41 2.4.3. Diagnosis of depression according to DSM-IV and ICD-10.............45 2.4.4. Severity of depression according to DSM-IV and ICD-10................48 2.4.5. Core symptoms of depression.........................................................49 2.4.6. Problems in the diagnostic of depression related to hypersomnia...52 2.4.7. Epidemiology....................................................................................53 3 2.4.8. Theories about depression related to sleep abnormalities...............55 2.5. Hypersomnia and depression......................................................................59 2.5.1. Similarities........................................................................................59 2.5.2. Possible causes of depression.........................................................61 2.5.3. Prevalence of depression in narcolepsy..........................................64 2.5.4. Prevalence of depression in idiopathic hypersomnia.......................66 2.5.5. Key references related to depression and daytime sleepiness........66 2.6. Research questions and hypothesis............................................................68 3. EMPIRICAL PART I: “Depressive symptoms in narcolepsy with and without cataplexy and idiopathic hypersomnia”…………………..............................70 3.1. Introduction..................................................................................................70 3.2. Methods.......................................................................................................72 3.2.1. Participants......................................................................................72 3.2.2. Procedure and questionnaires.........................................................73 3.2.3. Statistical analysis............................................................................75 3.3. Results.........................................................................................................77 3.3.1. Demographic and clinical characteristics.........................................77 3.3.2. Depressive symptoms – Univariate analysis....................................79 3.3.3. Variables influencing depression- Multivariate analysis...................89 4. EMPIRICAL PART II: “Narcoleptics with depressive symptoms compared to patients with depression”.....................................................................................93 4.1. Introduction..................................................................................................93 4.2. Methods.......................................................................................................94 4.2.1. Procedure and questionnaires.........................................................94 4.2.2. Participants......................................................................................95 4.2.3. Statistical analysis............................................................................97 4.3. Results.........................................................................................................97 4.3.1. Medication use.................................................................................97 4.3.2. Comparison of mean scores and grading distribution of depressive symptoms in questionnaires..........................................98 4.3.3. Correlations between different measures of depression................102 4.3.4. Age and sex differences.................................................................106 4.3.5. Somatic and affective items: differences between groups.............107 4 4.3.6. Differences in the structure of depressive symptoms between narcoleptic and depressive patients...............................................110 5. EMPIRICAL PART III: “Factor analysis of Beck Depression Inventory in patients with narcolepsy”.......................................................................................113 5.1. Introduction................................................................................................113 5.2. Method.......................................................................................................115 5.2.1. Participants....................................................................................115 5.2.2. Procedure and questionnaire.........................................................115 5.2.3. Statistical analysis..........................................................................115 5.3. Results.......................................................................................................117 5.3.1. Somatic and cognitive items of BDI...............................................117 5.3.2. Exploratory factor analysis (EFAs).................................................118 6. DISCUSSION........................................................................................................121 6.1. Discussion empirical part I: “Depressive symptoms in narcolepsy with and without cataplexy and idiopathic hypersomnia”..................................121 6.1.1. Predictors of depressive symptoms...............................................121 6.1.2. Presence of cataplexy....................................................................122 6.1.3. Similarities with other studies.........................................................123 6.2. Discussion empirical part II: “Narcoleptics with depressive symptoms compared with patients with depression”...................................................124 6.2.1. Sleepiness......................................................................................124 6.2.2. Subjective and unspecified question: Do you feel depressed?......126 6.3. Discussion empirical part III: “Factor analysis of Beck Depression Inventory in patients with narcolepsy”........................................................128 6.3.1. Negative attitude toward self..........................................................128 6.3.2. Cognitive dimension.......................................................................129 6.4. Overall findings of all three studies............................................................130 6.4.1. Similar severity of depression in NC+ and NC-..............................130 6.4.2. Daytime sleepiness