Parkinson’s disease and drug addiction are polar opposite diseases, but both depend upon dopamine. Parkinson’s patients don’t have enough of it; drug addicts get too much of it.
“This could be what underlies addiction,” says Northwestern University.
“Dopamine normally helps you adjust the pressure on the brake and gas pedals. It helps you learn that when you see a red light at an intersection, you brake and when the green light comes on, you take your foot off the brake and depress the gas pedal to go.
“…a healthy brain balances the urge to do something and the urge to stop….”
“Parkinson’s disease patients, who have lost the neurons that release dopamine, have their foot perpetually stuck on the brake.”
… but dopamine released by drugs leads to abnormal ‘go’ circuits and weak ‘stop’ circuits, resulting in an uncontrollable drive to ‘go’ and seek drugs.