What is the neurochemistry behind feelings of happiness?

Key Points to Remember

The ancient Greeks were pioneers in linking the body's physical state with our emotional responses. They proposed the theory of the four humors — yellow bile, black bile, blood, and phlegm — to explain human personality variations [source: Wilson]. Every person contains all four humors, and an imbalance, whether excessive or insufficient, could define prominent personality traits.

Even though the notions of phlegm and bile as bodily humors have been debunked over time, after 2,400 years, the connection between the body and emotions has resurfaced. In modern neuroscience, it is now proposed that happiness, like any other emotion, arises from the electrochemical processes in the brain triggered by external stimuli.

This breakthrough is part of the larger neuroscience revolution, which marks the fifth major shift in our understanding of humanity. The earlier revolutions, initiated by Copernicus, Darwin, Freud, and the discovery of DNA, laid the groundwork for the first four [source: Ramachandran]. The fifth revolution is inspired by Francis Crick's "astonishing hypothesis," which argues that "'you,' your joys and sorrows, your memories and your ambitions, your sense of personal identity and free will, are in fact no more than the behavior of a vast assembly of nerve cells and their associated neurons" [source: Crick].

This concept is supported by the 1960s discovery of a reward system in the brains of rats, and later in humans. Stimulating this system activates a series of brain regions that trigger the release of chemicals associated with pleasure. Central to this system is the nucleus accumbens, which plays a role in the feelings of happiness, such as laughter and euphoria [source: Cardoso].

The nucleus accumbens receives what can be seen as fuel for pleasurable feelings from the ventral tegmental area (VTA), which reacts to signals of pleasure from the cerebral cortex. The VTA sends a surge of the neurotransmitter dopamine to the nucleus accumbens and other regions in the reward system, a substance that is closely tied to the sensation of pleasure.

Additional brain areas complete the reward system, shedding light on the purpose not only of the reward center, but potentially the foundation of happiness itself. During a reward response, the prefrontal cortex becomes activated, focusing the individual’s attention and eventually conditioning the person to repeat the behavior that resulted in the reward.

When we enjoy a favorite food, feel comforted by another person’s touch, or experience a small victory in daily life, the cerebral cortex interprets this as a reward-worthy stimulus. From an evolutionary perspective, this stimulus provides some advantage. Essentially, our brains train us to repeat the actions that led to such pleasurable experiences. Emotions like happiness, therefore, act as motivators that increase an organism's likelihood of survival.

The exact way we experience pleasure from hormones like dopamine remains unclear. To date, science has demonstrated a correlation between dopamine and pleasure, primarily through tests where blocking or reducing the neurotransmitter led to diminished sensations of pleasure or pleasure-driven actions like eating. Additionally, we have the ability to anticipate pleasurable experiences, and dopamine levels rise during such anticipation, further supporting our drive to engage in behaviors that bring us joy.

However, happiness is not merely a feeling of pleasure; it is far more intricate. Studies have also linked other hormones, including progesterone, oxytocin, and testosterone, to different aspects of happiness, such as fostering a sense of well-being and creating deeper connections with others.