A close relationship exists between Aβ generation and the opioid system, as dysfunction of the opioid receptors causes retardation of endocytosis and degradation of the BACE1 enzyme; this enzyme is required for generating monomeric forms of Aβ, including Aβ42, which further aggregates into bioactive conformational species and is responsible for initiation of toxicity in AD (Hampel et al., 2020). This evidence concerns the gene BACE1 and Alzheimer disease.