We examined the co-occurrence of certain diseases with PD as reflected by the cooccurrence of the concepts in the documents of the CAS Content Collection (Figure ). Dementia and inflammation are between the expected co-occurrences. Several studies have shown that patients with PD suffer frequently from depression. Moreover, depression has been proposed to be a risk factor for PD. Inflammation has been commonly associated with both depression and neurodegeneration. Proinflammatory cytokines cause modifications in serotonin and dopamine neurotransmission leading to depression and PD. Yet the precise mechanism underlying the relationship between depression and PD remains unclear. Relationship between PD and diabetes has been reported more than three decades ago and confirmed by multiple studies later on. PD and diabetes share similar dysregulated pathways such as inflammation, mitochondrial dysfunction, impaired autophagy and insulin signaling , as well as certain genetic and environmental risk factors . Medications used to treat diabetes have indicated promise in alleviating motor symptoms in PD patients. Studies have reported association between cancer and PD, indicating a decreased risk of PD among most of the cancer types, e.g., analysis have shown that diagnosis of PD is associated with al 27% decreased risk of cancer ; another study reported a 17% decreased risk of cancer in PD patients . Prostate, lung, bladder, colorectal, blood and uterus cancers have been reported as the most reduced in PD patients. 100