Since I’ve started working on this project, many people have asked me if Parkinson’s disease is “genetic or environmental”. One of the most frequently cited studies on this question looked at twin brothers: identical twins versus fraternal twins. If one twin got Parkinson’s, would the other twin get it as well?
If Parkinson’s was genetic, we would expect both identical twin brothers to get Parkinson’s more often than both fraternal twin brothers. Why is this? Because identical twins share much more genetic information than fraternal twins, who share as much genetic information as regular brothers. More genetic information means more likelihood that both identical twins will share traits, including disease risk, that are caused or influenced by heritable factors.
So what did the study find? …read more