We read with interest the article by Southwick et al1 in the April 1993 issue of the Archives. Using intravenous yohimbine hydrochloride, the authors induced panic attacks in 70% and flashbacks in 40% of 20 subjects suffering from chronic posttraumatic stress disorder (PTSD). It is unclear, however, if their conclusion that panic disorder and PTSD share a common neurobiology is not, at least in part, a reflection of a lack of specificity in their assessment procedure. Furthermore, the applicability of their findings to the majority of people suffering from PTSD needs to be questioned.
Rainey et al2 reported the effect of intravenous lactate in seven Vietnam veterans with a history of flashbacks, six of whom met DSM-III criteria for both PTSD and panic disorder, and one with a history of PTSD meeting DSM-III criteria for panic disorder at intake. All of these subjects reported flashbacks after lactate infusion.
Safadi G, Bradwejn J. Relationship of Panic Disorder to Posttraumatic Stress Disorder. Arch Gen Psychiatry. 1995;52(1):76-77. doi:10.1001/archpsyc.1995.03950130076011