失智症的精神行為症狀（behavioral and psychological symptoms of dementia, BPSD）定義為在失智症患者身上出現的感覺、想法、情緒或行為的異常。它易造成病人與照顧者的困擾，常可預測預後較差、認知功能減退與疾病病程較快、生活品質下降與照護成本增加。當阿茲海默症患者出現精神行為症狀，第一步先排除是否與身體或內科疾病因素有關。接下來是詳細評估症狀的特色，先用非藥物治療（如行為治療）改善症狀，並教導患者與照顧者如何處理。若非藥物治療的效果有限，才考慮藥物治療。根據症狀屬性不同，有幾項基本原則：使用抗憂鬱藥物治療情緒障礙；使用抗精神病藥治療精神病症狀；使用抗癲癇藥物治療非精神病狀的激動行為。而且要定期檢討持續用藥的必要性。由於藥物皆有其可能副作用，如抗精神病藥可能增加中風、感染、死亡之風險，加上老年人生理狀況改變，故臨床醫療人員在治療精神行為症狀時，須綜合多方訊息，審慎評估藥物之療效及風險。

Behavioral and psychological symptoms of dementia (BPSD) are defined as abnormal perception, thought, emotion and behaviors in patients with dementia. BPSD produce significant distress in both patients and caregivers, predict poor prognosis, rapid cognitive decline and disease progression, poor quality of life and increased cost. When facing BPSD, the first step is to exclude any physical or medical factors that can contribute to these symptoms, and then assess the nature and relevant factors involved in the process of BPSD. Start non-pharmacological treatment first, if without success, consider pharmacological treatment. The basic principles are: use antidepressants for mood symptoms, antipsychotics for psychotic symptoms and anticonvulsants for non-psychotic agitation. Periodic evaluation is mandatory for the necessity of continuous prescription. Owing to many potential adverse drug reactions (e.g. antipsychotics related stroke and death in dementia), physicians should take into account not only efficacy, but also safety concern and effectiveness.