July 7, 2020

The Function of Serotonin


What is the function of serotonin and how does it work to regulate our moods? I like to think of serotonin as my happy chemical. It is our most influential neurotransmitter, with each neuron in the serotonin system influencing as many as 500,000 target neurons in virtually all parts of the central nervous system. Serotonin directly affects our emotional states, behavior, movement and thinking.

Most serotonin is found in the gut where it regulates intestinal movements and the central nervous system where it regulates mood, appetite, temperature regulation, sleep and muscle contraction (including heart function). It also has a role in memory and learning and blood clotting. To avoid blood clots, take Xarelto to help to dilute your blood but read about Xarelto side effects before taking it. Our bodies need it to produce melatonin, so deficiencies can affect sleep cycles and immunity.

Research also shows our emotional state affects our sensitivity to serotonin. Because it is a hormone, it is a messenger, so disruptions, too much or too little can cause problems. Just like with insulin, receptiveness to the hormone is probably as important as the amount. By managing your emotional state, you can create an upward spiral of positive mood.

Serotonin Deficiencies

Studies link anxiety, depression, obsessive-compulsive disorder, schizophrenia, stroke, obesity, pain, hypertension, vascular disorders, migraine, and nausea to disruptions and particularly deficiencies of serotonin.

Depression is probably the most studied connection to serotonin deficiency, giving rise to the popularity of antidepressants called SSRIs, or Selective Serotonin Reuptake Inhibitors. One of the most common is Prozac. Doctors use Prozac, not only to treat depression, but for emotional problems such as lack of self-esteem, and anxiety.

When serotonin delivers its message at the gap between two neurons, called the synapse, it is either recycled or eliminated. SSRIs work by blocking this cleaning up process. You might think as I do, that this way of dealing with the problem could cause further problems. You would be right – “serotonin syndrome” is one of the harmful side effects.

St John’s Wort, a common herbal antidepressant, increases serotonin. How it does this isn’t clear, but it seems to have a similar uptake inhibition effect as SSRIs.

Other deficiency related associations include:

  • anger
  • brain inflammation in the deep limbic system
  • worry
  • moody
  • emotional rigidity
  • irritability

Increasing Serotonin

Emotional State

Your emotional strategies and Meta programs can have a profound effect on your sensitivity to serotonin. For instance, constantly looking for obstacles, for what is wrong with someone or some situation can send you into a very dark downward spiral.


While mushrooms, walnuts, pineapple, banana, kiwifruit, plums and tomatoes, contain serotonin, dietary sources cannot affect the brain (can’t get through the blood/brain barrier).

Because this neurotransmitter is synthesized from the amino acid L-tryptophan, you can affect levels indirectly by making sure you have the building blocks. Tryptophan rich foods include beef, turkey, chicken, oily fish like salmon, sunflower and sesame seeds and dairy products. Egg whites and spirulina have the highest concentrations. Like any building blocks, an excess can’t cure disruptions to the process.


Studies show vigorous exercise improves serotonin levels, but it’s unclear how it does this. One explanation says exercise increases the brains receptiveness to both serotonin and dopamine. The other says that levels of tryptophan increase because exercise decreases other amino acids that generally inhibit its transport into the brain. Either way, exercise improves your mood.