Some recent studies conclude the existence of a anti-reward circuit in our brain, a network of brain regions that causes negative emotional and physical reactions to things, in return to the brain's reward circuit.
The anti-reward system, then, basically what it does is that we feel unhappy. But why is there something like that in our brain?
While the reward system is not known in as much detail, the anti-reward system would involve certain regions of the tonsil and terminal stria (near the thalamus), and would depend on the neurotransmitters corticotropin-releasing factor (CRF) and dinorphine As Dean Burnett explains in his book The Happy Brain:
Abnormally high levels of CRF have been detected in the cerebrospinal fluid of people who have died of suicide, and dinopyrins have been repeatedly linked to stress and depression. It is believed that both neurotransmitters cause dysphoria, a deep state of discomfort and depression that is basically the opposite of euphoria.
Why is there something that makes us feel uneasy in the brain? What is known is that this system is activated when the reward circuit does. That is, we experience unease when we experience pleasure.
It is as if this unease reduced our degree of pleasure a little, as if it prevented us from going too high. As an aftertaste of distaste that controls our enthusiasm and does not "restrain". However, there are more hypotheses:
Or it may be simply to keep the opposite system operational. Many biological functions are controlled by two opposite systems, as in the case of the sympathetic and parasympathetic nervous systems and there must then be a basal level of activity in either of them to keep the cells that compose them alive.
The interesting thing about this delicate balance, in which the faithful of the balance tries neither to lean too much to one side or the other is that it can be damaged, for example, if we use some drugs in excess, therefore, perhaps, many addicts end up with a system of reward that barely responds to stimuli: the anti-reward system is exaggeratedly overactive. Therefore, many chronic consumers do not get high enough for pleasure to feel "normal" again, because the drug is the only thing that slows the anti-reward system.