Dean Burnett in Psyche:
Our ability to experience pleasure, as in the fundamental sensation of something being enjoyable or ‘nice’, is a product of what’s known as the ‘reward pathway’, a small but crucial circuit found deep within the brain. As you might suspect, dopamine is the main neurotransmitter involved in the function of the reward pathway. Hence why it’s often called the dopamine reward pathway. So, if the activity of dopamine in the brain makes a vital contribution to the sensation of pleasure, and pleasure is a key aspect of happiness, then it stands to reason that boosting your dopamine levels will make you happier, right?
There’s a superficial logic to this way of looking at things. Unfortunately, the logic doesn’t hold given the daunting complexity and interconnectedness of our brains. There’s a wealth of evidence to demonstrate that simply ‘boosting your dopamine’ doesn’t automatically result in happiness. And it comes via research into Parkinson’s disease.
More here.