Dans la maladie d'Alzheimer, l'expression des troubles psychologiques et comportementaux est précoce et spécifique des stades lésionnels

The symptomatic association of “depression”, “agitation”, and “irritability of mood” may remain in a steady state for a few months before the appearance of verbal episodic memory impairment, which is characteristic of hippocampus involvement. “Irritability” seems to specifically characterise the initial phase of AD. On the other hand, two BPSSD are characteristic of the late stages of AD: “sleep disorder” and “hallucinations”.