What is serotonin? Is it linked to depression, meaning explained, how to increase levels, what does it do

A review of 17 previous studies found no evidence of a link between depression and low serotonin

A major analysis undertaken by University College London (UCL) has found there is no link between serotonin and depression.

UCL complered an “umbrella analysis” of 17 reviews and studies and discovered no link that low serotonin levels can cause depression.

People with depression are often prescribed antidepressants known as selective serotonin reuptake inhibitors (SSRIs) which help balance serotonin levels in the brain.

Researcher Joanna Moncreif said: “The implication of our paper is that we do not know what [SSRI] antidepressants are doing.”

Here’s everything you need to know about what serotonin is and what the latest analysis has found.

What is serotonin?

Serotonin or 5-hydroxytryptamine (5-HT), is a naturally occurring chemical messenger that works as a neurotransmitter to carry signals between the nervous system and your brain.

It helps with mood, memory, sleep and your gut to aid healthy digestion.

Low levels of serotonin have been linked to depression.

Signs of low serotonin can include: disrupted sleep, mood changes, trouble with memory and loss of appetite.

A selection of antidepressants (L-R) Wellbutrin, Paxil, Fluoxetine and Lexapro (Pic: Getty Images)A selection of antidepressants (L-R) Wellbutrin, Paxil, Fluoxetine and Lexapro (Pic: Getty Images)
A selection of antidepressants (L-R) Wellbutrin, Paxil, Fluoxetine and Lexapro (Pic: Getty Images)

What does serotonin mean?

According to Oxford languages, serotonin is defined as: “a compound present in blood platelets and serum, which constricts the blood vessels and acts as a neurotransmitter.”

How is serotonin linked to depression?

Analysts have linked serotonin to depression since the 1960s.

The serotonin hypothesis proposes the idea that low serotonin levels are caused by a chemical imbalance in the brain which leads to depression.

Current theories suggest that both biological, psychological and social factors play a role in developing depression, but the most popular treatment is SSRIs antidepressants.

These medications work by increasing the levels of serotonin in the brain.

The latest analysis by UCL suggests that serotonin may not play a role in depression and that these medications “are working through a placebo effect.”

However, Johan Lundberg from the Karolinska Institute in Sweden says that the analysis was limited.

Lundberg explains that it didn’t distinguish between ongoing depression and episodes of depression.

He explained: “It is key to separately analyse data from studies that examine the same patients when ill and when in remission, to have optimal conditions to examine the hypothesis.”

In a statement from the Royal College of Psychiatrists regarding the study they said: “Antidepressants are an effective, NICE-recommended treatment for depression that can also be prescribed for a range of physical and mental health conditions.”

Adding: “Antidepressants will vary in effectiveness for different people, and the reasons for this are complex. We would not recommend for anyone to stop taking their antidepressants based on this review, and encourage anyone with concerns about their medication to contact their [family doctor].”

How can you increase serotonin levels?

There are a few ways you can increase your serotonin levels naturally.


Whilst you cannot get serotonin from food directly you can get a boost from the amino acid tryptophan.

Normally found in high-protein foods like salmon and turkey.

Current studies suggest to get the most benefit, it’s best to eat foods rich in tryptophan alongside carbohydrates.


Exercising is a great way to help increase your levels of serotonin.

Studies have shown the best exercise is aerobics, so it’s the perfect excuse to sign up for a dance or pilates class.

Bright Light

Many experience low serotonin levels during wintertime.

Seasonal Affective Disorder (SAD) is a type of depression that comes during autumn and winter when daylight levels are low.

Spending time in daylight or sunshine helps, with researchers suggesting that you spend 10 to 15 minutes outside every day.

Another popular option is a SAD light, which works to replicate sunlight and improve your serotonin levels.


Massages have been shown to help increase serotonin and dopamine levels in the brain.

Not only are they great for overall relaxation, they also help to decrease cortisol levels.