Null hypothesis of husband-wife concordance of Parkinson's disease in 1,000 married couples over age 50 in Spain.

While the search for environmental neurotoxins as causal factors of Parkinson's disease (PD) continues, we have found no concordance in 1,000 married couples over age 50 in Spain. In addition, it has been possible to identify a structural grouping of similar chemical characteristics that is repeated in the majority of organic compounds that can induce parkinsonism. These compounds have a structural relationship with the dopamine molecule. The principal epidemiological aspects of PD have a preliminary rational explanation.