Secondary depression in panic disorder and agoraphobia. I. Frequency, severity, and response to treatment.
Lesser IM, Rubin RT, Pecknold JC, Rifkin A, Swinson RP, Lydiard RB, Burrows GD, Noyes R Jr, DuPont RL Jr. Arch Gen Psychiatry. 1988 May; 45(5):437-43.