Page 33 - The clinical aspects and management of chronic migraine Judith Anne Pijpers

Introduction
Migraine and depression are both rated among the top 20 of most disabling disorders by the World Health Organisation.1 Previous studies showed that persons with migraine have a fivefold higher risk of first-onset major depression than persons without migraine. In addition, persons with a lifetime depressive disorder have a threefold higher risk of first-onset migraine than persons without a depression diagnosis.2;3 This bidirectional association suggests a shared aetiology, which is supported by several studies indicating shared genetic factors in migraine and depression.4;5 Besides depression, there is an association between anxiety disorders and migraine as well.6 The economic impact of migraine is significantly compounded in patients with comorbid psychiatric conditions.7 Understanding the mechanisms underlying the comorbidity is important in order to gain more insight into the mechanism of both migraine and depression/anxiety and to develop specific preventive treatments. Previous studies in migraine defined depression using either categorical DSM- IV (Diagnostic and Statistical Manual of Mental Disorders) diagnoses or self- reported questionnaires. However, although DSM-IV categories are of great use in clinical practice, they have arbitrary boundaries, and show much overlap and comorbidity. Moreover, high heterogeneity of symptoms and severity within one diagnostic category is possible.8 Depression and anxiety severity scales based on self-reported questionnaires also have limitations: two similar scores may indicate different clinical subtypes due to the heterogeneity of the covered range of symptoms as multidimensionality of symptomatology is not taken into account. Consequently, measuring affective disorders with these tools may provide suboptimal phenotyping for clinical and biological (e.g. genetic) research. Thus, in a research setting, it may be more appropriate to study dimensions of depressive and anxiety symptoms in migraine patients as these seem to reflect more homogeneous disease entities.
Several attempts have been made to develop a dimensional model for depression. Within a dimensional approach, a patient is described in terms of scores on a range of coexisting different symptom domains, and not in terms of presence or absence of psychopathology.9 A well-known model is the tripartite model that accounts for the overlap between depression and anxiety.10 In this model the broad symptom dimension of negative affect covers symptoms of general psychological distress (e.g. lack of concentration or pessimism). High
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Affective disorders in migraine patients
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