Endogeneity and reactivity as orthogonal dimensions in depression.
Endogeneity and reactivity have long been considered polar opposites of a major dimension of depression. The present factor analytic study examines 35 distinct depressive symptoms in three depressed samples and supports the conceptualization of D. F. Klein (Endomorphic depression. Arch. Gen. Psychiatry, 31:447-454, 1974) that endogeneity and reactivity can be construed as orthogonal, independent dimensions. Symptoms consistently loading on an endogeneity factor are: 1) lacking in reactivity to environmental changes; 2)showing no interest in life; 3) retarded (slow, feeling tired, etc.); 4) feeling unable to act; 5) considering self lazy; 6) feeling helpless and powerless; and 7) perceiving depression as qualitatively different from ordinary sadness. Symptoms consistently loading on a reactivity factor are: 1) feeling that he or she is bearing troubles; 2) presence of precipitating stress; 3) crediting problems to excessive family and/or job responsiblitiies; 4) expressing concern for welfare of family and friends; 5) visceral symptoms; 6) feeling at "end of rope"; 7) having middle-of-the-night insomnia; and 8) showing self-pity. The results suggest a methodology for identifying depressives who are high-high, low-high, high-low, and low-low on the endogeneity and reactivity factors.