Anxiety as part of depression

Changes in diagnostic criteria have shown a trend towards a broader definition of depression. Thus, a number of patients who would previously have been considered to be suffering from anxiety states are now classified as having major depressive illness according to the criteria of the Diagnostic Statistical Manual III. Despite this, such patients show a good response to antidepressant drugs (compared to placebo) if their severity of depression is above 15 on the Hamilton depression scale. It therefore seems likely that there is a common biological substrate underlying both anxiety states and depressive illness, but this issue remains somewhat controversial. The suggestion that the 5-HT system is involved in the mediation of anxiety is considered. Further evidence is required before definite conclusions can be drawn, but it seems clear that anxiolytic activity is not dependent on sedative properties.