PROBLEM TO BE SOLVED: To provide a method of using p11 as a drug target as well as a tool for the diagnosis, treatment and development of p11/5-HT receptor-related disorders.SOLUTION: A method of diagnosing p11/5-HT receptor-related disorders includes steps of; determining a level of p11 in a biological sample from a subject and comparing the p11 level to a reference, where an abnormal level of p11 compared to the reference constitutes a positive diagnosis of the p11/5-HT receptor-related disorder; using p11 knock-out animals as well as p11 transgenic animals as models for development of novel psychotherapeutic agents; and selecting the p11/5-HT receptor-related disorder from a group consisting of depression, obsessive compulsive disorder, drug addiction, eating disorders, Alzheimer's disease, attention deficit disorder, attention deficit hyperactive disorder, mania, bipolar disorder, anxiety disorders, aggression, sleep disorders, sexual dysfunction and gastrointestinal disorders.SELECTED DRAWING: None【課題】p11/5-HT受容体関連障害の診断、処置および開発のための薬物標的および手段としてのp11の使用を提供する。【解決手段】p11/5-HT受容体関連障害を診断する方法であって、対象からの生物学的試料中のp11のレベルを決定し、ここで参照と比較してp11の異常レベルがp11/5-HT受容体関連障害の陽性とする工程、p11ノックアウト動物およびp11トランスジェニック動物を新規精神治療薬の開発のためのモデルとして使用する工程、ならびにp11/5-HT受容体関連障害がうつ病、強迫性障害、薬物依存、摂食障害、アルツハイマー病、注意欠陥障害および注意欠陥多動性障害、躁病、双極性障害、不安障害、攻撃性、睡眠障害、性機能障害および胃腸障害からなる群から選択される工程を含む。【選択図】なし