Addiction to nicotine is due to high intrinsic levels of dopamine.

Smokers are less likely to develop Parkinson's disease (PD) than is true of non-smokers, and PD is the only disease inversely related to smoking. PD is associated with a reduced level of dopamine. Although nicotine can affect the receptors, including dopamine receptors, it seems unlikely that use of nicotine is protective in PD. An alternative explanation is that just as PD is associated with a lower than normal level of dopamine, addiction to smoking is linked with a higher than normal level of dopamine. This high innate level of dopamine facilitates addiction to nicotine.