Parkinson's disease (PD) is the second most common neurodegenerative disorder after Alzheimer's, afflicting 1% of the population above the age of 65. The number of people with PD has icreased in the last 30 years, and it is expected to grow in the next years, due to the ageing of population and possible environmental factors. PD symptoms are both motor and non-motor: to tremor, rigidity and bradykinesia, the most representative symptoms of the disease, a variety of automatic nervous system dysfunction, sleep disorders, depression and anxiety should be added. The symptoms are caused by a lack of dopamine, a neurotransmitter produced by the brain cells that are attacked and depleted by PD.