This study investigate the effect of high-intense aerobe exercise training (HIT) on clinical and physiological parameters (anxiety, somatisation, cortisol, alpha amylase, "mismatch negativity", loudness dependence auditory evoked potentials) in patients with generalized anxiety disorder (GAD). Half of patients will receive HIT, while the other half will receive aerobe exercise of low intensity.

Generalized anxiety disorder (GAD) is a prevalent psychiatric condition and characterized by worrying of several topics of the daily life as well as stress-induced somatic symptoms (e.g. headache or musculoskeletal pain). Disturbed monoaminergic neurotransmission, changes in central information processing and altered levels of stress markers were reported as to be biological correlates of GAD or other stress-related disorders. Cognitive behavioral therapy is the first-line treatment in GAD, but it seems to be less effective than in other anxiety disorders. There is, however, some evidence for an anxiolytic activity of aerobe exercise. In this context, different forms of aerobe training were found to be associated with significant reduction of clinical symptoms in panic disorder, agoraphobia or social phobia as well as a normalisation of some of its pathophysiological markers.

In this study, 20 patients with GAD will receive a high-intensive aerobe training (HIT, 6 HIT-sessions of 20 minutes within a period of 12 days). Additionally, 20 GAD-patients will undergo a less intense aerobe training matched regarding frequency and duration of sessions. Prior to the first training session, after completing the training (day 12) and 30 days after baseline, symptoms of anxiety and somatisation will assessed by using established questionnaires. Moreover, saliva samples and electroencephalogram (EEG) will performed at the same times of assessment in order to evaluating changes of cortisol, alpha amylase, "mismatch negativity" and loudness dependence auditory evoked potentials.

We hypothesize, that GAD-patients which undergo HIT, will show a stronger and more sustained improvement of both, clinical symptoms and formally altered electrophysiological and endocrinological parameters.

Inclusion Criteria:

• Generalized Anxiety Disorder (GAD) according to the 5th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5)
• Appropriate abilities to communicate and to complete the questionnaires
• Written informed consent
• Possibility of regular attendance at the training sessions

Exclusion Criteria:

• Other severe mental conditions than GAD (e.g. schizophrenia, severe depressive episode, addiction)
• Acute suicidality
• Epilepsy or other disorders of the central nervous system (e.g. tumor, encephalitis)
• Contraindications to aerobe exercise training
• Cardiovascular diseases
• Start or modification of an anxiolytic pharmacotherapy within the last four weeks
• Current psychotherapy