The neuroprotective effects of nasally administered insulin that have already been noted in slowing down the progression of neurological conditions, such as AD, anxiety, depression, eating disorders, olfactory epithelium injury, Parkinson's disease, Phelan-McDermid syndrome and substance addition, are independent of peripheral insulin concentration [6, 26, 29, 30, 35]. This evidence concerns the gene INS and major depressive disorder.