Dopamine vs. Serotonin: What To Know About These Two "Feel-Good" Neurotransmitters

At some point, we've all taken stock of our mental health and realized we could benefit from a little boost. That little boost we all seek and crave isn't so much a salary raise or new relationship itself—it's the chemicals behind it.  

Dopamine and serotonin are neurotransmitters, which are "chemical messengers that relay important messages between cells and attach to specific receptors on target cells," says Aimee Harris-Newton, Psy.D., a double-board certified integrative and interventional psychologist. Specifically, dopamine takes care of neurons that control movement and coordination, and it works highly on the reward system. 

These two crucial neurotransmitters can also affect depression or other mood disorders, and an imbalance in both neurotransmitters can affect bodily functions and can lead to different medical conditions, says Sanam Hafeez, Psy.D., a neuropsychologist and director of Comprehend The Mind. They don't exist in a vacuum but rather as part of a larger ecosystem: "Although serotonin and dopamine affect different parts of the brain, they often work together. For example, if serotonin levels decrease, then dopamine levels will increase," Hafeez says.

Serotonin and dopamine are often referred to as "happy hormones" because they both play a significant role in regulating mood and emotion, according to Hafeez. As mentioned, though serotonin and dopamine affect different parts of the brain, they often work in unison (meaning if serotonin levels go down, then dopamine levels go up). "Also, both serotonin and dopamine affect appetite and impulsivity while serotonin typically suppresses hunger, whereas dopamine stimulates it, and serotonin inhibits impulsivity, and dopamine enhances it," she says.

Both serotonin and dopamine are highly affected by sunlight. Horowitz says that 10 to 20% of our serotonin is made in the pineal gland1, which is sensitive to sunlight. If daylight is scarce or we're stuck indoors, she says the pineal gland will produce the hormone melanin, which suppresses the production of serotonin, thereby causing our mood to take a nosedive. This explains why we get the blues (or seasonal affective disorder) when it gets dark earlier in the fall and winter. Sunlight also triggers the release of dopamine. Horowitz explains that when exposed to outdoor light, specialized eye cells connect to other cells that release dopamine. Additionally, she says that when your skin absorbs sunlight and produces vitamin D, it creates a cycle that triggers the production of dopamine as well as serotonin. 

While the two neurotransmitters function in similar ways, they do pose significant differences. Harris-Newton says increased amounts of serotonin hinder impulsive behavior, while dopamine ramps it up. Hafeez adds that in some cases, low serotonin levels can lead to an overproduction of dopamine—this is because serotonin appears to inhibit dopamine production. Because dopamine enhances reward-seeking behavior, she explains impulsivity might indirectly arise from low serotonin. 

Speaking of impulsive behavior, drugs activate both dopamine and serotonin in our brains in different ways, according to Hafeez. "When people engage in recreational drug use, serotonin levels increase, which makes people feel very good. This high is the primary reason people continue taking them. They want to experience the high again. However, this fluctuation of serotonin also contributes to the depression and anxiety people feel when going through withdrawal." 

Whereas serotonin and drug use elicits euphoria, dopamine and drug use reinforces the reward-seeking behavior, says Hafeez, which increases the likelihood of repeating the activity and as a result, addiction and painful withdrawal symptoms. 

What *doesn't* dopamine do for the body? Hafeez says it's released every time you anticipate or experience pleasure. "For example, if you love brownies, your dopamine levels will most likely increase simply from the smell while they bake in the oven. When you finally eat the brownie, the release of dopamine reinforces your love for brownies and encourages you to continue to crave brownies," she says. If the balance of dopamine in the body is level, Hafeez says you're likely to feel focused, happy, and motivated. If dopamine levels are too low, you're likely to feel the opposite: distracted, depressed, and indifferent.

In addition to balancing mood, serotonin assists in digestion, metabolism, sleeping and waking, appetite, hormonal activity, libido, blood clotting, and regulating body temperature, according to Harris-Newton. While serotonin is present in the brain, 90% of the body's serotonin is made in the gut, she says. (You can read more about the connection between gut and brain health here.)

"Our digestive tract is filled with an entire ecosystem of bacteria, and we're learning that the more quantity and diversity of bacteria, the less you're likely to experience illness," says Horowitz. "If our gut bacteria's balance is disturbed, not only does our digestion suffer, but so does our mood. One theory is that a lack of bacteria and bacteria diversity leads to a decrease in the production of serotonin5. When your gut health is poor, your body is less capable of converting amino acids from food into the neurotransmitters in your brain."

If psychiatric medication isn't part of your mental health care plan, there's lots you can do to boost your serotonin levels naturally: Horowitz says tryptophan, found in foods like milk, turkey, fish, spinach, seeds, and eggs, can help boost your serotonin levels by making 5HTP, an amino acid that boosts the neurotransmitter's production. Vitamins and minerals like iron, zinc, and vitamin B3, B9, and C can also facilitate that building of serotonin, she says.

Although Hafeez says research has not confirmed that low levels of serotonin cause depression or anxiety, we do know that SSRIs help treat symptoms of both. "SSRIs prevent serotonin from being reabsorbed, so more serotonin remains present in the brain, which causes people's moods to increase," she says.

Although dopamine is most closely associated with reward and pleasures like food, sex, gambling, and shopping, Hafeez says it can also affect other bodily functions such as sleep, memory, motor control, and digestion, and even play a role in the development of Parkinson's disease.