Depression and anxiety disorders

Abstract Depression and anxiety disorders are, by far, the most common psychiatric disorders, with a lifetime prevalence estimated as high as 16% for major depressive disorder alone. Similar figures have been reported for anxiety disorders. In the widely used Diagnostic and Statistical Manual of Mental Disorders , major depressive disorder (MDD; also termed unipolar depression) has been brought under the heading of ‘mood disorders’, together with dysthymia (i.e. chronic mild depression), various types of bipolar disorder (or manic depressive disorder), and some additional, sometimes provisional, diagnoses. Similarly, since the 1980s, anxiety disorders have been grouped together in the DSM. This category includes ‘pure’ (non-phobic) anxiety disorders, in which patients may experience anxiety symptoms without clearly identifiable external cues, and phobic disorders, the symptoms of which are triggered by specific objects or situations. Non-phobic anxiety disorders are panic disorder (PD) and generalized anxiety disorder (GAD), both formerly lumped together under the name of anxiety neurosis. Phobic disorders include agoraphobia (which usually occurs in the context of panic disorder), social phobia, and the so-called specific phobias, e.g. for animals (snakes, spiders) or specific situations (elevators, airplanes). Finally, obsessive compulsive disorder (OCD) and post-traumatic stress disorder (PTSD) have been classified as anxiety disorders, again with a few residual categories for completeness’ sake. Comorbidity among anxiety disorders is high, not only for PD and agoraphobia, but also for PD and GAD, and for PD and social phobia. In addition, depressive episodes are common in anxiety disorders, and panic attacks frequently co-occur in MDD. Although this would suggest a shared predisposition and/or pathogenetic mechanism between depression and anxiety disorders, their aetiology is still insufficiently clear, with the exception of PTSD.