In DSM-5 (American Psychiatric Association, 2013) anxiety disorders are included under the heading of mood disorders. This is because of the noted interlinkages of anxiety and depression (Clark & Watson, 2006). Whereas in DSM-IV-TR (American Psychiatric Association, 2000) panic disorder was linked with agoraphobia, it is now recognised that some patients have symptoms of agoraphobia without panic. The two disorders are now separated in DSM-5 and both agoraphobia and panic disorder can be separately recorded.

Fear is a universal and essential emotion. Without it the human race would have fallen over cliffs and failed to run from sabre-tooth tigers until we became extinct. However, not all fear is rational and based on a threat to survival. People differ in the background level of fear (trait anxiety) and the situations which provoke fear (state anxiety). All of us have some morbid fears which we know to be irrational but which we cannot stop. These fears may be embarrassing but they do not lead us to change our lifestyle in any major way. They can be seen as on a continuum with phobic disorder.

Phobias have been defined as morbid fears which are involuntary, cannot be reasoned away and lead to avoidance of the feared object or situation (Marks, 1969). Clearly, they do overlap with morbid fears.