SynopsisThis research was aimed at studying the rate of action of tricyclic drugs in depressive disorders, specifying the behavioural effects associated with recovery, and predicting clinical response. The research design involved comparison of a recovered group with a group treated for the equivalent four weeks, who showed minimal to no response. The findings indicated significant differences in baseline characteristics between responders and non-responders. Further, the drugs were found to act early in the responders, within the first week of treatment. Specific changes at one week which distinguished responder and non-responder groups occurred in the disturbed affects, and in cognitive functioning. Improvements also occurred in somatic symptoms, but these latter changes were general and not associated with later recovery. At 2½ weeks, all facets of the depressed condition showed positive change in the responders. Implications of the results for assessing rate of tricyclic drug actions, their effects on the interaction of affect and neurochemistry, and the practical application of the results for the clinical situation, are discussed.