Dopamine and serotonin are chemical messengers, or neurotransmitters, that help regulate many bodily functions. Dopamine is involved in movement, coordination, and a person’s feelings of pleasure and reward. Serotonin is involved in emotions as well, but it also affects digestion and metabolism.

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People sometimes refer to dopamine and serotonin as the “happy hormones” due to the roles they play in regulating mood and emotion.

They are also involved in several mental health conditions, including low mood and depression.

Dopamine and serotonin are involved in similar bodily processes, but they operate differently. Imbalances of these chemicals can cause different medical conditions that require different treatments.

This article looks at the differences and similarities between dopamine and serotonin, their relationship, and their links with medical conditions and overall health.

Neurons in the brain release dopamine, which carries signals between neurons.

The body uses dopamine to create chemicals called norepinephrine and epinephrine.

Dopamine plays an integral role in the reward system, a group of brain processes that control motivation, desire, and cravings.

Dopamine levels also influence the following bodily functions:

Serotonin is another neurotransmitter present in the brain.

However, more than 90% of the body’s total serotonin resides in the enterochromaffin cells in the gut, where it helps regulate the movement of the digestive system.

In addition to aiding digestion, serotonin is involved in regulating:

Although both dopamine and serotonin relay messages between neurons and affect mood and concentration, they have some other distinct functions.

Dopamine, for example, relays signals between neurons that control body movements and coordination.

This neurotransmitter also plays a role in the brain’s pleasure and reward center, and it drives many behaviors. Eating certain foods, taking illegal drugs, and engaging in behaviors such as gambling can all cause dopamine levels in the brain to spike.

Higher levels of dopamine can lead to feelings of euphoria, bliss, and enhanced motivation and concentration. Therefore, exposure to substances and activities that increase dopamine can become addictive to some individuals.

Like dopamine, serotonin can influence people’s moods and emotions, but it also helps regulate digestive functions, such as appetite, metabolism, and gut motility.

Both dopamine and serotonin are neurotransmitters with positive associations.

They are also neuromodulators, meaning that, unlike other neurotransmitters, they are able to communicate with many neurons that are near as well as far away from the dopamine or serotonin release site.

As neuromodulators, dopamine and serotonin also send signals that last longer than the signals of other neurotransmitters.

Neurotransmitters do not act independently. They interact with and affect each other to maintain a careful chemical balance within the body. There are strong links between the serotonin and dopamine systems, both structurally and in function.

In some cases, however, serotonin may inhibit dopamine production, which means that low levels of serotonin can lead to an overproduction of dopamine. This may lead to impulsive behavior due to the role that dopamine plays in reward-seeking behavior.

Dopamine and serotonin also have opposite effects on appetite. While serotonin suppresses it, low levels of dopamine can stimulate hunger.

Serotonin also inhibits impulsive behavior. By contrast, dopamine enhances impulsivity.

Having abnormal levels of either dopamine or serotonin can lead to several different medical conditions.

Both neurotransmitters can affect mood disorders, such as depression. Imbalances can also result in distinct conditions that affect different bodily functions.

The following sections cover these conditions in more detail.

Dopamine

Dopamine deficiency may play a significant role in the following conditions and symptoms:

Dopamine also plays a role in motivation and reward-driven behaviors.

The SLC6A3 gene provides instructions for creating the dopamine transporter protein. This protein transports dopamine molecules across neuron membranes.

A medical condition that health experts call dopamine transporter deficiency syndrome or infantile parkinsonism-dystonia occurs when mutations in the SLC6A3 gene affect how the dopamine transporter proteins function.

Dopamine transporter deficiency syndrome disrupts dopamine signaling, which impacts the body’s ability to regulate movement.

For this reason, dopamine transporter deficiency syndrome produces symptoms similar to those of Parkinson’s disease, including:

Serotonin

Having too much serotonin can lead to a potentially life threatening medical condition called serotonin syndrome or serotonin toxicity.

This condition can occur after taking too much of a serotonergic medication or taking multiple serotonergic medications at the same time.

In 2016, the Food and Drug Administration (FDA) provided a list of serotonergic medications. Aside from selective serotonin reuptake inhibitors (SSRIs), some of these include:

According to the FDA, opioid pain relievers can interact with serotonergic medications, which can lead to a buildup of serotonin or enhance its effects in the brain.

Dopamine and serotonin both affect the sleep-wake cycle. This cycle is regulated by the brain’s pineal gland, which has receptors for both neurotransmitters.

In response to light and darkness signals from the eyes, the pineal gland secretes the hormone melatonin, which causes sleepiness.

Dopamine decreases the production of norepinephrine and thus has a significant impact on wakefulness, according to research.

In a 2022 study on mice, researchers also found that dopamine had the ability to put the mice into rapid eye movement (REM) sleep. The same mechanism may be at play in people living with narcolepsy, as a rise in dopamine may be a factor in uncontrolled daytime sleep episodes.

Serotonin promotes wakefulness as well as sleepiness. A person needs serotonin to produce melatonin. However, serotonin also suppresses REM sleep, which may lead to sleep disorders.

Most of the body’s serotonin is produced in the gut. Serotonin stimulates the small intestine to perform contractions that move food through the digestive tract.

More serotonin is released when a person digests something to which they have an allergic reaction or that contains harmful bacteria. This causes faster contractions, which may result in diarrhea or vomiting.

Conversely, constipation may occur due to a low level of serotonin in the gut.

Like serotonin, dopamine helps move food through the digestive tract. It also helps control the production of insulin in the pancreas, and it protects the gut’s mucosal lining, which may prevent peptic ulcers.

Both dopamine and serotonin can impact mental well-being.

Dopamine

Although dopamine alone may not directly cause depression, having low levels of dopamine may cause specific symptoms that health experts associate with the condition.

These symptoms can include:

  • lack of motivation
  • difficulty concentrating
  • feelings of hopelessness and helplessness
  • loss of interest in previously enjoyable activities

Serotonin

Researchers have linked low levels of serotonin with mood disorders, such as depression and anxiety.

Serotonin may cause depression in some cases, although multiple factors beyond biochemistry also contribute, such as:

  • genetics and family history
  • lifestyle and stress levels
  • environment
  • additional medical conditions

Having low serotonin levels may increase a person’s risk of developing depression. Serotonin medications — such as SSRIs, which increase the availability of serotonin in the brain — may help treat depression.

SSRI medications include:

The optimal range for serotonin in the blood is generally 50–220 nanograms per milliliter.

The optimal range for dopamine in the blood is generally less than 30 picograms per milliliter.

Having too much or too little dopamine and serotonin can impair communication between neurons. This may lead to the development of physical and mental health conditions.

For instance, a low level of dopamine can cause symptoms associated with depression. A high level of serotonin can lead to serotonin syndrome, a potentially life threatening condition.

Below, we answer some common questions regarding dopamine and serotonin.

Do dopamine and serotonin make a person happy?

People often call dopamine and serotonin the “happy hormones,” because they promote mental well-being.

Dopamine, also known as the “feel-good” hormone, is associated with the brain’s reward system and produces pleasant sensations.

Serotonin can help increase happiness by alleviating depression and anxiety.

Can dopamine and serotonin also cause depression?

Dopamine and serotonin themselves may not cause depression. However, researchers believe that an imbalance of these neurotransmitters is a major factor in the development of depression.

A dopamine imbalance can cause depression symptoms, such as apathy and feelings of hopelessness, while a serotonin imbalance can affect the processing of emotions.

How can a person increase dopamine and serotonin?

A person can raise dopamine and serotonin levels with medications such as antidepressants.

To naturally boost dopamine and serotonin levels, eat a balanced diet with foods containing tryptophan, the protein that produces these neurotransmitters.

Tryptophan-rich foods include:

Doing the following can also increase dopamine and serotonin levels:

The neurotransmitters dopamine and serotonin regulate similar bodily functions but produce different effects.

Dopamine regulates mood and muscle movement and plays a vital role in the brain’s pleasure and reward systems.

The body stores the majority of serotonin in the gut. Serotonin helps regulate mood, body temperature, and appetite.

Having too much or too little of either neurotransmitter can cause psychological and physical symptoms.