SINCE THE SEASONAL inclination of occurrence of panic attacks was proposed in 1989,1 several reports related to seasonal panic disorder have been reported. However, only one case that has been treated successfully with light therapy has been reported.2
This report describes the case of a 47-year-old man: a healthy postal worker. He had experienced his first panic attack, characterized by palpitation, a choking sensation, chills, and terror, at age 35 in April. At 40 years old, he visited our hospital, where his case was diagnosed as panic disorder based on DSM-IV-TR criteria. The administration of sulpiride, lorazepam, alprazolam, and selective serotonin reuptake inhibitor were ineffective for his attacks. At 47 years old, a detailed re-interview revealed that his panic attacks occurred mainly during June–September, summer in Japan, during his postal duties; panic attacks seldom occurred off-duty during the daytime. Summer-related seasonal panic disorder was diagnosed. The average urination frequency during the daytime (08.30 hours–17.30 hours) during his postal work was zero or once, although he had no renal disease. He drank no water despite his thirst while on duty. Prior to June, he was directed to drink sufficient water to maintain urination frequency of at least 4–8 times per day. His panic attacks did not occur at all for over 8 months from June. Written informed consent was obtained from the patient.
Normal frequency of urination is zero to one time at nighttime, one time per 3–5 h during the daytime, and 4–8 times per day.3 Dehydration without renal disease causes decreased urination frequency by decreased peripheral perfusion.4 Viscerosensory information is conveyed to the amygdala by a major pathway – downstream from the nucleus of the solitary tract – according to Gorman's neuroanatomical hypothesis of panic disorder.5 On the other hand, the region of the nucleus of the solitary tract is a target of dehydration-sensitive corticotrophin-releasing hormone neurons.6 Accordingly, it was assumed that dehydration induced panic attacks in the present case.
Unfortunately, laboratory data that might indicate sodium levels around the time of the panic attacks were not obtained. Nevertheless, based on detailed examination during an interview, it was inferred that the panic attacks occurred during periods of dehydration. Water supply therapy, by which the frequency of urination is maintained as at least 4–8 times per day, can be useful in some patients with summer-related seasonal panic disorder.