Dopamine and serotonin are both neurotransmitters. Neurotransmitters are chemical messengers that regulate countless functions and processes in your body, from sleep to metabolism.

While dopamine and serotonin affect many of the same things, they do so in slightly different ways. Here, we give a run-down of the differences between dopamine and serotonin when it comes to depression, digestion, sleep, and more.

Like other mental health conditions, depression is a complex condition that’s caused by a number of factors. Both dopamine and serotonin play a role in depression, though experts are still trying to figure out the details.

Dopamine

Dopamine plays a big role in motivation and reward. If you’ve ever worked hard to reach a goal, the satisfaction your feel when you achieve it is partly due to a rush of dopamine.

Some of the main symptoms of depression include:

  • low motivation
  • feeling helpless
  • a loss of interest in things that used to interest you

Experts believe these symptoms are linked to a dysfunction within your dopamine system. They also believe this dysfunction might be triggered by short- or long-term stress, pain, or trauma.

Serotonin

Researchers have been studying the link between serotonin and depression for more than five decades. While they initially believed that low serotonin levels caused depression, they now know that isn’t the case.

The reality is more complicated. While low serotonin doesn’t necessarily cause depression, increasing serotonin through the use of selective serotonin reuptake inhibitors (SSRIs) is one of the most effective treatments for depression. However, they do take some time to work.

Among people with moderate to severe depression, 40 to 60 percent of people only report an improvement in their symptoms after they’ve taken SSRIs for six to eight weeks. This suggests that simply increasing serotonin isn’t what treats depression. Instead, research has suggested that SSRIs increase positive emotional processing over time, resulting in an overall shift in mood.

Another factor is that researchers have found that depression is associated with inflammation in the body. SSRIs have an anti-inflammatory effect.

THE MAIN DIFFERENCE Dopamine system dysfunction is linked to certain symptoms of depression, such as low motivation. Serotonin is involved in how you process your emotions, which can affect your overall mood.

Dopamine and serotonin also both play roles in psychological conditions other than depression.

Dopamine

Nearly all pleasurable experiences, from eating a good meal to having sex, involve the release of dopamine. That release is part of what makes some things addicting, such as:

Experts evaluate something’s potential to cause addition by looking at the speed, intensity, and reliability of the dopamine release it causes in your brain. It doesn’t take long for your brain to associate certain behaviors or substances with a rush of dopamine.

Over time, your dopamine system may be less reactive to the substance or activity that used to cause a big rush. For example, someone might need to consume more of a drug to achieve the same effects that a smaller amount used to provide.

Experts also believe that a dysfunction of the dopamine system plays a role in:

Serotonin

In a 2014 review, serotonin was also linked to several other conditions, including:

More specifically, the researchers found low serotonin binding among people with obsessive-compulsive disorder (OCD) and social anxiety disorder. This results in less available serotonin in the brain.

In addition, they found that people with autism are more likely to have lower levels of serotonin in certain areas of the brain.

Bipolar disorder was also associated with altered serotonin activity, which may influence the severity of someone’s symptoms.

THE MAIN DIFFERENCE There’s a close link between dopamine and how you experience pleasure. Dysfunction of the dopamine system might also contribute to bipolar disorder and schizophrenia. Serotonin affects emotional processing, which can have significant effects on mood.

It’s not just your brain — you also have dopamine and serotonin in your gut, where they play a role in digestion.

Dopamine

Dopamine’s role in digestion is complex and poorly understood. However, experts do know that it helps to regulate the release of insulin from your pancreas.

It also affects movement in your small intestine and colon to help move food through your system. In addition, dopamine has a protective effect on the mucosal lining of your gastrointestinal tract, which may help to prevent peptic ulcers.

More research is still needed to fully understand how else dopamine may affect our guts.

Serotonin

Your gut contains around 95 percent of your body’s serotonin. It’s released when food enters the small intestine, where it helps to stimulate contractions that push food through your intestines.

Your gut releases extra serotonin when you eat something containing harmful bacteria or an allergen. The extra serotonin makes the contractions in your gut move faster in order to get rid of the harmful food, usually through vomiting or diarrhea.

Low serotonin in your gut, on the other hand, is associated with constipation.

Based on this knowledge, research has found that serotonin-based medications can help treat several gastrointestinal conditions, such as irritable bowel syndrome. They’ve also been used to treat nausea and vomiting caused by chemotherapy.

THE MAIN DIFFERENCE While both dopamine and serotonin are found in your gut, serotonin plays a much larger role in digestion. It helps to stimulate contractions in your gut that move food through your intestines.

Your sleep-wake cycle is regulated by a small gland in the brain called the pineal gland. The pineal gland receives and interprets light and darkness signals from the eyes. Chemical messengers translate these signals into the production of melatonin, a hormone that makes you feel sleepy.

The pineal gland has receptors for both dopamine and serotonin.

Dopamine

Dopamine is associated with wakefulness. Drugs that increase dopamine levels, such as cocaine and amphetamines, typically increase alertness. In addition, diseases that decrease dopamine production, such as Parkinson’s disease, often cause drowsiness.

In the pineal gland, dopamine can stop the effects of norepinephrine, a neurotransmitter involved in producing and releasing melatonin. When dopamine appears, your pineal gland makes and releases less melatonin, causing you to perk up.

A 2012 study also found that sleep deprivation decreases the availability of certain types of dopamine receptors. With fewer receptors, dopamine doesn’t have anywhere to attach to, making it hard to stay awake.

Serotonin

Serotonin’s role in regulating the sleep-wake cycle is complex. While it plays a role in maintaining sleep, it can also prevent you from falling asleep. How serotonin affects sleep depends on the part of the brain it comes from, the type of serotonin receptor it binds to, and several other factors.

In a part of your brain called the dorsal raphe nucleus, high serotonin is associated with wakefulness. However, an accumulation of serotonin in the area over time may put you to sleep.

Serotonin is also involved in preventing rapid eye movement (REM) sleep. Studies have shown that increasing serotonin through the use of SSRIs reduces REM sleep.

While serotonin seems to both induce sleep and keep you up, it’s a chemical precursor to melatonin, the main hormone involved in sleep. Your body needs serotonin from your pineal gland in order to produce melatonin.

THE MAIN DIFFERENCE Both dopamine and serotonin play a role in your sleep-wake cycle. Dopamine can inhibit norepinephrine, causing you to feel more alert. Serotonin is involved in wakefulness, sleep onset, and preventing REM sleep. It’s also required to produce melatonin.

Dopamine and serotonin are two neurotransmitters that play important roles in your brain and gut. An imbalance in your levels of either one can have effects on your mental health, digestion, and sleep cycle.

While they both affect a lot of the same parts of your health, they do so in distinct ways the experts are still trying to understand.