Whether you’re looking to address your mood changes, sleep patterns, or libido, there’s one place you can start: discovering the difference between dopamine and serotonin, and the profound ways in which they both affect our brain and body. 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. According to Alyssa Kirby Horowitz, N.D., a naturopathic doctor, “serotonin and dopamine are not the be-all and end-all of anything, but they play a larger role. In a Broadway theater, they might be the main stars but without the background dancers and lights, it might be the [most underwhelming] product.” She explains that serotonin and dopamine enable our organs to communicate with one another. 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. Finally, they also both play a profound role in digestion. The serotonin made in the gut plays a role in our intestines’ ability to contract, signals pain, prompts nausea, and causes other digestive issues, which explains why antidepressants can lead to digestion-related side effects, according to Horowitz. Similarly, she says 50% of our dopamine is made in the gut2, and while it sends signals from the brain, it acts as a messenger to help contract the colon muscles. And of course: Food is very much thy medicine. “Our mood affects our nutrition choices just as much as the opposite is true,” says Horowitz. 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. While they both affect appetite, they do so in contrasting ways: Low dopamine levels are said to boost appetite3 thanks to the release of the appetite stimulant ghrelin, while low serotonin levels reduce appetite thanks to the release of the appetite suppressant leptin (this may explain uncharacteristically extreme eating patterns in those with depression—low dopamine may lead to overeating, while low serotonin makes it tough to stomach a full meal). Low dopamine famously plays a role in mood changes. “We see it as the chemical that’s in charge of our motivation, so if any of those pathways are deficient, compromised, or dysfunctional, you’ll have a huge decrease in motivation, which is a symptom of depression,” says Horowitz. “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.” Serotonin is also associated with our body’s digestion process by decreasing our appetite as we eat, explains Hafeez. “Without serotonin, we would struggle to identify when we are full and should stop eating. Additionally, when we eat something toxic to our bodies, serotonin levels increase, which causes the irritating food to expel from our body quickly.” That “runner’s high” isn’t an old wives’ tale, either: Just 30 to 45 minutes of sustained aerobic activity boosts serotonin, giving you that natural post-cardio relaxed, unstoppable feeling. 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. And of course, recreational drugs that artificially spike the release of dopamine, like cocaine, can lead to addiction since they fool the brain into thinking it’s at its baseline level. “Recreational drug use significantly affects dopamine levels, which contributes to addiction and withdrawal,” says Hafeez. “It can produce feelings of euphoria; however, these are only temporary while the drugs remain in the system.” Her first novel PRETTY WEIRD: Overcoming Impostor Syndrome and Other Oddly Empowering Lessons was published by Skyhorse Publishing and distributed by Simon & Schuster in May 2021.
