Anxiety and Anxiety Disorders

Anxiety is one of the important normally and regularly occurring emotions. Some of the actual public health problems like anxiety disorders are based on the pathology of feelings. Anxiety disorders comprise a heterogeneous group of disorders and each of these disturbances has a different etiology and outcome, and different physiological characteristics. Among the most important influences are actually genetic disposition, environmental impact upon one individual, and acute stressors that result in adaptational changes. Considering a large body of findings, several monoamine neurotransmitters and anxiogenic or anxiolytic-like neuropeptides are involved in the regulation of fear and anxiety. Anxiety is one of the important normally and regularly occurring emotions, which can be observed throughout all human cultures and in several animal species. Some of the actual most prominent medical and public health problems like anxiety disorders or depression are based on the pathology of feelings (Damasio and Carvalho, 2013). While recent data show that the basic facial expression of emotions is also modulated by culture-specific influences, fundamental emotional expressions such as anxiety or fear originate presumably from the beginning of human ontogeny as biologically hardwired and universal signals (Jack et al., 2013). Anxiety disorders comprise a heterogeneous group of disorders and each of these disturbances has a different etiology and outcome, and different physiological characteristics. Depending on actual classification rules according to the DSM 5 (2013), panic attacks and panic disorder, phobias, social phobia, and generalized anxiety disorder are summarized in anxiety disorders. In contrast to former classifications, posttraumatic stress disorder and obsessive compulsive disorder are no longer included, despite the fact that anxiety is a relevant dimension of these disorders. Moreover, anxiety has to be differentiated from fear and the so-called stress responses. Anxiety derives from complex origins and among the most important influences are actually genetic disposition; environmental impact upon one individual, especially early adverse events; and acute stressors that result in adaptational changes. Considering a large body of findings, several monoamine neurotransmitters, for example, gamma-aminobutyric acid (GABA), serotonin, and noradrenalin, are involved in the regulation of fear and anxiety. In addition, an increasing variety of either anxiogenic neuropeptides like corticotropin-releasing factor (CRF), cholecystokinin tetrapeptide (CCK-4), vasopressin, and others, or anxiolytic-like neuropeptides like neuropeptide Y (NPY), neuropeptide S, and atrial natriuretic peptide (ANP) are most important in the modulation of anxiety. Several neurobiologic findings also stem from investigations in humans by eliciting panic attacks. Panic attacks are unique in the spectrum of psychiatric disorders; since their core psychopathology is temporally limited, they can be provoked under laboratory conditions and can in part be conditioned. Due to the experimental character of these investigations, close comparisons with experiments in animals can be drawn. Hence it has been proposed that panic disorder involves the same pathways that support conditioned fear in animals. However, while induction of panic anxiety has been studied intensively, little is known about the intrinsic mechanisms for the termination of panic and anxiety. Anxiety or fear is, in addition to happiness, sadness, anger, disgust, and desire, one of the important normally and regularly occurring emotions, which can be observed throughout all human cultures and in several animal species (Ekman, 1982), but the facial expression of such basic emotions is also modulated by culture-specific influences. Anxiety per se is a complicated concept since several difficulties arise in defining this emotion and, in addition, it has to be differentiated from fear and stress (see below). Anxiety occurs, besides in anxiety disorders, also comorbid in several other psychiatric conditions. Moreover, anxiety refers to a variety of other emotional experiences, for example, apprehensiveness, tension, and agitation, which occur also in other emotional states. Anxiety is defined by subjective, behavioral, and physiological characteristics. Anxiety involves the experience of dread and apprehensiveness, and the physiological reactions of anxiety usually include trembling, sweating, elevated heart rate and blood pressure, and increases in muscle tone. Anxiety is defined as pathological when occurring inadequately or with much more pronounced severity and debilitating features. An additional defining criterion in standardized diagnostic manuals is the concomitant occurrence of anxiety and avoidance. Representatives for these diagnostic entities, in which anxiety is the leading symptom, are panic disorder and generalized anxiety disorder. Anxiety is experienced in phobic disorders when the subject is confronted with the feared stimulus, which results in its avoidance. One of the reasons for the declaratory confusion of the term anxiety is its psychological similarity to fear and its vegetative similarity to stress. Similar to anxiety, fear also includes the experience of dread, and fear seems to be largely included into the concept of anxiety. Moreover, anxiety and fear induce similar bodily reactions, which include the socalled stress responses. In general, these can be separated in active responses, known as ‘fight or flight’ reactions or behavioral inhibition, like freezing. The accompanying stress-related sequelae can again be divided into two large entities: the excitatory fight or flight response postulated by Cannon (1929), and the endocrine stress concept raised by Selye 804 International Encyclopedia of the Social & Behavioral Sciences, 2nd edition, Volume 1 http://dx.doi.org/10.1016/B978-0-08-097086-8.27006-2 (1956). Complementarily, the results of several studies indicate that stress involves brain structures, which also mediate the perception of anxiety such as amygdala, hippocampus, and other limbic structures (see below). Differentiation of Anxiety Both anxiety and fear are regularly experienced within a range of normal emotional responses of everyday life. Specifically, fear is necessary to achieve personal growth and individual freedom during ontogeny.