This week, my guest article on the neuroscience education site Knowing Neurons examines why drugs that enhance levels of the neurochemical dopamine make people more impulsive – that is, more likely to choose short-term gratification rather than think in the long-term. This concerns both recreational drugs such as cocaine and alcohol, as well as medical treatments for Parkinson’s disease, which either boost dopamine production (eg. L-DOPA) or stimulate dopamine receptors (eg. apomorphine). In my piece, I also explore the scientific evidence that individuals who are innately more impulsive than others might have stable life-long differences in various components of their brains’ dopamine systems.