This invention relates to a drug for preventive and/or therapeutic of stress diseases that administers (1S)-2-acetyl-1-(4-chloro-2-methoxyphenyl)-5-fluoro-1,2,3,9-tetra-hydro-spiro[β-carboline-4,1'-cyclopropane] by specific dosage capable of achieving necessary TSPO occupancy in brain for the expression of medicinal effect.本發明係有關一種壓力性疾病之預防及/或治療用醫藥,其特徵為以可達成藥效表現所需之腦內TSPO占有率的特定用量來投予(1S)-2-乙醯基-1-(4-氯-2-甲氧基苯基)-5-氟-1,2,3,9-四氫螺[β-咔啉-4,1’-環丙烷]。