A prospective, randomized, double-blinded, placebo-controlled, pilot study of 16 enrolled patients (15 with Parkinson’s disease and 1 with multiple system atrophy diagnosis) reported that intranasal insulin administration for a 4-week period improved cognitive and motor performance in PD patients, while there was a lack of disease progression in the multiple system atrophy case, compared to intranasal sterile saline administration [42]. Here, INS is linked to Parkinson disease.