Think you know about serotonin? Think again

a blackboard with the chemical diagram of serotonin

Meet serotonin, the ancient molecule that has an enormous influence on your body. Working as a neurotransmitter in the brain, serotonin plays a role in almost all functions of the central nervous system, including mood, anxiety, aggression, cognition, sexual impulses and hunger. 

Scientists are still investigating the wide range of effects serotonin has on the body, as well as what happens when you have too much or don’t have enough. What they’re discovering is that we’re only just beginning to scratch the surface.

Read on to find out more.

The two lives of serotonin

Serotonin is the most widely distributed neurotransmitter in the brain. It is involved in a wide range of essential brain functions, including emotion regulation, cognitive control and motor activity (movement). 

At the same time, serotonin also acts as a so-called peripheral hormone in many other organs. Peripheral serotonin is involved in the regulation of heart rate, cell growth in the liver, bone and pulmonary arteries, the function of the immune system and brain development, as well as many other processes. Recent research shows it could also enhance nutrient absorption and nutrient storage too.

What can go wrong with serotonin?

Interestingly, there’s only a tiny amount of serotonin-producing neurons in the human body compared to the total number of neurons but their influence is huge. The gastrointestinal tract is the largest producer of serotonin in the body and most serotonin is transported in the bloodstream via blood platelets.

When there is a problem with the production or transportation of serotonin in the body, it can lead to severe health outcomes. 

Mental health

Serotonin is perhaps best known for its role in mental health and mental illness. Serotonin deficits are reported in severe depression, suicide and alcoholism. 

The problem is, the link between low levels of serotonin and depression have been oversimplified in the past. Many people think that mental illness is a result of too little serotonin in the brain but in reality, serotonin’s role in emotion regulation is much more complicated than it seems.

Gastrointestinal disease

Problems with the regulation of serotonin in the gut have been linked to a diverse range of GI disorders. Serotonin is linked to common gut health problems including inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS). Changes in serotonin signaling have also been shown to be associated with celiac disease, colorectal cancer and diverticular disease.


The relationship between serotonin and cancer is extremely complex. Research shows that it is dependent on the concentration of serotonin. For instance, higher amounts of serotonin can stimulate growth in aggressive cancers. On the other hand. low doses of serotonin can inhibit tumour growth by decreasing the blood supply to the tumour. In some cases, serotonin inhibitors have been successfully used to prevent cancer cell growth too.

Serotonin syndrome

Recently, Serotonin Syndrome has become a major concern for healthcare professionals due to the rapid increase in antidepressant use across the US and Europe. 

This illness is caused by an excessive increase in the concentrations of serotonin in the brain, to the point that it becomes toxic. In mild cases, symptoms of serotonin syndrome include nervousness and insomnia but in severe cases it can cause delirium and fever. Left untreated, serotonin toxicity can be life-threatening.

The role of serotonin in the body

Serotonin is an ancient molecule that has been central to the maintenance of life for billions of years. While most people are familiar with serotonin and its role in regulating emotions and mood, the influence of serotonin in the body is much more complex that it first seems.

As well as impacting mood, research has shown that serotonin regulates sleep, appetite, sexual activity, and other important brain functions. At the same time, problems with serotonin production and regulation have been linked to a range of different diseases, including GI disorders, cancer and mental illness. Next time you go to sleep, eat or feel your mood changing, say hello to serotonin!