認知症における妄想

Delusions in Dementia

妄想は認知症の行動・心理症状の中でも代表的な症状である。頻度が高いのは被害妄想群で，物盗られ妄想，嫉妬妄想，見捨てられ妄想などがある。被害妄想を生じる患者では，社会的信念の形成過程に障害があり，注意バイアス，帰属バイアス，結論への飛躍バイアス，心の理論の障害などが影響すると考えられる。認知症にみられる被害妄想の神経解剖学的基盤として，内側前頭前皮質など社会的認知に関わる神経回路（社会脳）の障害が示唆されている。

Abstract

Delusion is a common neuropsychiatric symptom in dementia, especially in Alzheimer disease and dementia with Lewy bodies. Persecutory delusions are the most common, and include delusions of theft, jealousy, and abundant. Patients with persecutory delusions have impairment of the psychological processes mediating the formation and maintenance of normal social beliefs. Several disordered psychological processes such as attentional bias, attributional bias, jumping-to-conclusions reasoning bias, and theory of mild deficit may contribute to the delusion formation. Cognitive processes involving information about self, others, and social interaction are required in social cognition. Damage of the neural circuitry involved in social cognition (“social brain”), such as the medial prefrontal cortex, may be a neuroanatomical basis for persecutory delusions in dementia.