Ires Ghielen

32 Chapter 2 to make a clear distinction between autonomic symptoms caused by anxiety and PD-related autonomic dysfunction will probably prove futile. The diagnostic criteria for anxiety disorders underline that physical symptoms comprise an integral part of the syndrome ‘anxiety’ [26]. Moreover, PD-related autonomic symptoms and anxiety frequently co-occur and overlap in symptomatology [2, 24], and there is an interplay between anxiety and somatic symptoms [2, 3, 24]. The development of autonomic failure in PD may lead to a pathophysiological predisposition towards somatic symptoms of anxiety. This hypothesis is supported by research in non-PD patients suffering from autonomic failure. For example, in patients with pure autonomic failure, hyperventilation causes a larger decrease in blood pressure than in healthy controls [27, 28]. In a case-report on a patient with pure autonomic failure who experienced dizziness during emotional stress, a significant decrease in blood pressure after stressful events was demonstrated [29]. Moreover, PD patients with failure of both the sympathetic and parasympathetic nervous system had higher levels of anxiety and depression than healthy controls or de novo PD patients [30]. One may therefore expect that the presence of autonomic failure in PD patients gives rise to a stronger physical response to anxiety. The presence of anxiety is also associated with an increase in motor symptoms in PD [6-8]. Vice versa, PD-related motor symptoms, such as wearing-off, can give rise to anxiety: a substantial number of PD patients suffers from situational anxiety, with phobic avoidance related to fear of experiencing off-periods or freezing [3]. The clinical finding that many PD patients with response fluctuations experience anxiety and autonomic symptoms during wearing-off [6, 31, 32], suggests that dopaminergic transmission is involved in the etiology of both motor and non-motor symptoms of PD [33, 34]. These findings make the distinction between anxiety and other motor and non-motor symptoms of PD appears artificial. In line with this, the MDS task force on rating scales for PD recommends an “inclusive approach” when rating possible symptoms of anxiety in PD patients, without trying to attribute them to either anxiety or other PD-related symptoms [35]. The finding of an affect subscale of the BAI, that is not influenced by motor or autonomic symptoms, might nevertheless be relevant for research purposes. Moreover, our results can be useful in the development of new measures for anxiety in PD. This study has some limitations. The only measure of anxiety in this study was the BAI. The BAI can be used to assess symptoms of anxiety, but is not a diagnostic instrument. Moreover, the BAI is more suitable for measuring episodic anxiety than the non-episodic anxiety that occurs in generalized anxiety disorder [18], which is one of the most prevalent anxiety disorders in PD patients [2]. Strengths of the present study are the large number of patients included, and the homogeneity of