What exactly is serotonin, what is a depression, and how are the two connected?

However, this is only partly accurate, as serotonin does not simply switch on happiness. Above all, it helps stabilize mood and maintain inner balance.

Around 90 percent of the serotonin in the body is produced in the intestinal mucosa. The body also produces smaller amounts in the brain. There, serotonin acts as a messenger substance for the nervous system—also known as a neurotransmitter. Messenger substances are called this because they transmit messages from one nerve cell to the next. This messenger substance:

• supports impulse control,
• dampens aggression,
• regulates the sleep-wake rhythm,
• stimulates bowel movement, and
• influences body temperature, blood pressure, the perception of pain, and muscle tension.

Serotonin is formed from the amino acid L-tryptophan. The body cannot produce L-tryptophan itself, so it must be ingested through food. Good sources include eggs, dairy products, poultry, fish, tofu and other soy products, legumes such as lentils and chickpeas, nuts, seeds, oatmeal, and cocoa.

A dark mood that feels heavy, makes daily life strenuous, and drains the color out of things that used to be fun. The main characteristics, which occur in almost every case, are a depressed mood, little to no interest or joy, and a lack of drive. These symptoms persist for at least two weeks, nearly every day, and noticeably take over one's life.

Many people find it difficult to fall asleep or wake up early. For some, it is the other way around: they sleep a great deal and still feel tired. Concentration is difficult. Thoughts spin in circles. Feelings of guilt emerge, even when there is no good reason for them. Appetite and weight can change. Some people eat much less, while others eat more. Physical symptoms also occur, such as headaches, stomach aches, or back pain without a clear cause.

Depression has nothing to do with weakness. It is an illness in which many things in the body and brain have fallen out of balance. Stress, distressing experiences, genetic predisposition, and physical illnesses can all play a role. No one chooses a depression. And no one needs to feel ashamed of it.

For many years, the simple formula was: too little serotonin causes depression. While this sounds plausible, it is not scientifically proven. A major study found no convincing evidence that a low serotonin level directly causes depression.

Depression develops based on a multitude of factors. A role is played, for example, by genetic predisposition, individual experiences, current stress, and physical illnesses.

However, even though the old serotonin hypothesis of depression is on shaky ground, serotonin-based medications can still help relieve symptoms.

Now the question naturally arises: "Can you measure serotonin levels?" Short answer: yes, you can measure serotonin (or its breakdown products). Laboratories can either measure serotonin directly in the blood or its main breakdown product (5-HIAA) in urine. For depression, however, this is generally of no use.

Why? Serotonin acts primarily in the brain, and blood values do not accurately reflect what is happening there. Furthermore, serotonin levels fluctuate depending on the time of day, diet, and medications. When dealing with depression, these tests rarely help with making medical decisions. Much more important than numbers are the symptoms themselves, their duration and severity, and potential triggers. Even more crucial is their treatment.

Depression is highly treatable, and the effectiveness of treatment options is thoroughly researched.

The diagnosis is made by doctors or psychotherapists. Making a diagnosis means carefully evaluating what is going on. This takes place during a calm conversation where you share how you are feeling, how long you have felt this way, and how severely it impacts your daily life. The specialists then evaluate the depression based on medical criteria and propose a treatment plan.

Talk therapies are proven to be highly effective for depression. Cognitive Behavioral Therapy (CBT) is particularly well-researched. In CBT, you learn to recognize unhelpful thought patterns, take step-by-step action, and regulate difficult emotions. Many people quickly experience an increase in drive and self-efficacy.

For severe and long-lasting depression, medication—specifically an antidepressant—is prescribed in addition to psychotherapy to help lift the mood. Antidepressants do not contain serotonin themselves, but they alter how nerve cells handle serotonin in the brain.

For those who want to know more precisely how different types of antidepressants alter the way nerve cells interact with serotonin:

• SSRIs (e.g., sertraline, citalopram): Block the reuptake of serotonin into the nerve cell, allowing more serotonin to remain available between the cells.
• SNRIs (e.g., venlafaxine, duloxetine): Act in a similar manner.
• NaSSAs (e.g., mirtazapine): Block specific binding sites (receptors) and thereby indirectly enhance the effect of serotonin.

deprexis is a recognized online program that offers people with depression helpful information, individualized dialogues, and effective exercises. The content of this Digital Health Application (DiGA) is based on Cognitive Behavioral Therapy (CBT). Your family doctor can prescribe deprexis for you, and your health insurance covers the costs. The best part: it can be used easily at any time and in any place.

Daily life tips do not replace professional treatment. However, they do help strengthen your daily routine. The following tips are scientifically proven and easy to implement:

Regular bedtimes help you find your inner rhythm. Go to bed at the same time whenever possible and wake up at a similar time in the morning. Air out your room, keep it dark, and place your phone out of reach. Morning light signals to the brain: "The day is here." This is a natural way to increase serotonin, as good sleep supports the regulatory circuits in the brain.

Exercise has a mood-lifting effect, even during depression. Start small by walking for 10 minutes a day at first, and then build up to 30 minutes of brisk walking. If you like, you can add short strengthening exercises. In this way, the body releases substances that strengthen nerve connections. This can indirectly support the effect of serotonin on the psyche.

A protein-rich diet provides tryptophan, a precursor to serotonin. Combined with complex carbohydrates and dietary fiber, this works well for the gut. Think of vegetables, whole-grain products, legumes, nuts, and drinking sufficient fluids.

Chronic stress increases the hormone cortisol. The connection between cortisol and serotonin is complex: too much stress can strain sleep, appetite, and mood. Taking short breathing breaks, keeping fixed meal times, maintaining regular social contacts, and enjoying small moments of pleasure work to counteract stress.