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Re: Experimental Affective Symptoms in Panic Disorder Patients

Dear Editor: In a recent issue of The Canadian Journal of Psychiatry, Overbeek and colleagues assessed depression and aggression symptoms beyond anxiety symptoms in panic disorder (PD) patients (1). They administered a gas mixture of 35% CO2 and 65% O2 to 25 patients with PD, 9 of whom also met the criteria for a comorbid major depressive disorder (MDD). It is suggested that, in addition to anxiety, CO2 challenge induces depressive and aggressive symptoms, specifically in PD patients with comorbid depression