Serotonin helps brain cells communicate.

Serotonin is a chemical messenger made by your body. In the brain, it helps nerve cells communicate.

These cells are called neurons. Their messages help regulate mood, among other functions.

This page explains SSRI medicines for depression, starting with serotonin.

A brain cell releases serotonin into a tiny gap.

An electrical signal reaches the end of a neuron. Small packets inside release serotonin into the gap between cells.

Watch the teal dot leave its packet. The cell stays still. This close meeting point is called a synapse.

Serotonin changes a cell’s activity through receptors.

A receptor is a protein that responds to serotonin. Serotonin attaches briefly, triggering changes inside the receiving cell.

A doorbell button works similarly: a press starts something inside. Different serotonin receptors can raise or lower a cell’s activity.

Transporters take serotonin back into the releasing cell.

A transporter is a protein that moves serotonin into the cell. This return trip is called reuptake.

Watch the dot return through the transporter. Removing serotonin from the gap helps limit its signal.

An SSRI blocks serotonin’s return route.

SSRI means selective serotonin reuptake inhibitor. These medicines block serotonin transporters. Sertraline and fluoxetine are examples.

Less serotonin is taken back up, leaving more available between cells. The drug changes serotonin signaling; it does not supply serotonin.

Depression has several contributing causes.

Depression can affect mood, sleep, and everyday life. Inherited traits, brain biology, life experiences, and physical health can contribute.

A simple serotonin shortage does not explain depression. A medicine helping someone does not prove what caused their illness.

Mood benefits usually take weeks.

Blocking reuptake begins before mood improves. Antidepressant benefits usually take four to eight weeks. Some changes appear sooner.

Scientists study slower changes in receptors and connections between cells. How these changes produce relief is still being worked out.

SSRIs help some people more than others.

For some people, depression symptoms ease and daily life gets easier. Others get little benefit or need a different treatment.

Benefits and side effects both matter. A clinician can help assess them over time.