HTR1A and major depressive disorder: Hasler et al. (193), and more recently, Goldstein and Klein (194) have published detailed reviews about both psychopathological (e.g., neuroticism, anhedonia, depressed mood, increased stress sensitivity), and biological (e.g., morning cortisol, tryptophan depletion, DEX/CRH, CRH dysfunction, hippocampal volume, and reduced 5HT1A receptor expression) endophenotypes for depression.