Alterations of Benzodiazepine Receptor Binding Potential in Anxiety and Somatoform Disorders Measured by [123]I-Iomazenil SPECT([123]I-Iomazenil SPECTを用いた、不安障害および身体表現性障害におけるベンゾジアゼピン受容体結合能の変化に関する研究)