These depressions are probably related to the manic-depressive group; nevertheless the symptoms and the course of the involution cases are sufficiently characteristic to justify us in keeping them apart as special forms of the emotional reaction.
To be included here are the slowly developing depressions of middle life and later years which come on with worry, insomnia, uneasiness anxiety and agitation, showing usually the unreality and sensory complex, but little or no evidence of any difficulty in thinking. The tendency is for the course to be a prolonged one. Arteriosclerotic depressions should be excluded.
When agitated depressions of the involution period are clearly superimposed on a manic-depressive foundation with previous attack (depression or excitement) they should, for statistical purposes, be classed in the manic-depressive group.