Zirbeldruese is somehow important

Spring: Why the serotonin cheers in the brain

The first sunny days are enchanting: a real spring awakening sets in. Not only is nature on the move, people are too. They jog through parks, ride a bike or go for a walk. Good weather puts you in a good mood, you want to get out into the gardens and street cafes. It's also nice that it's light longer.

What happens in spring: The bright light of the sun reaches the eyes and has already reached the outskirts of the brain. "There, the light stimuli trigger excitations that also reach the pineal gland in the hypothalamus (diencephalon) via the optic nerve. There they modulate the release of the hormone melatonin," explains Siegfried Kasper, director of the Clinic for Psychiatry and Psychotherapy at the Medical University of Vienna . The pineal gland converts the good mood hormone serotonin, which is formed in the brain during the day, into the sleep hormone melatonin in the dark of the night.

Melatonin makes you tired and depresses the mood. The conversion is carried out by enzymes that are slowed down by light. The bright morning sunlight therefore reduces the release of melatonin. At the same time, the brain stem becomes active as a factory of happiness. There are several core areas that are important for our emotional balance. Serotonin is produced in the so-called raphe nuclei and distributed throughout the brain. This neurotransmitter, which is necessary for the transmission of electrical impulses between the nerve cells, creates a balanced mood. At the same time, it dampens worries, grief and fears.

Happiness as a feeling

Another core, the substantia nigra, is the main production site for dopamine. Dopamine is important for movement and functions as a messenger substance between the nerve cells of the happiness and reward or motivation system (mesolimbic system) of our brain. If we see or experience something beautiful, for example in the park, this system signals "good". The happiness hormone dopamine is then activated. It is thanks to dopamine that we can look forward to flowering plants or chirping birds in spring and enjoy life. If more serotonin and dopamine are released, mood and drive increase. More exercise also has a positive effect on people's mood. So it comes to "spring feelings".

How positive the spring sun and the longer days have on the mood is noticed in particular by all those who suffer from winter depression every year. The intensity of the sunlight has a very positive effect on them. "People who previously felt a little down and had no drive suddenly feel good, are wide awake and active," says Kasper.

A lack of light in winter leads to changes in the serotonin balance in otherwise completely healthy people. Kasper and his colleagues used an imaging method, positron emission tomography, to observe that the intensity of solar radiation determines how strongly the serotonin docking points on the nerve cells bind the neurotransmitter to themselves. "We found that the binding of serotonin decreased by up to 30 percent after dark days. That clouded the mood," reports Kasper.

A light shower

Spring sunlight has the same effect as light therapy against winter depression. But while a so-called light shower releases around 10,000 lux, sunlight provides around 100,000 lux, "says the Viennese psychiatrist. How is the extremely positive effect of light on seasonally depressed people explained? About our internal clock. Early morning light inputs cause their internal clock to be disturbed gradually reprogrammed.

So spring awakens our spirits. But there are also people who initially do not feel a spirit of optimism, who get a tremendous craving for carbohydrates and just feel tired and exhausted. For Kasper, that's not surprising. Due to the changed lighting conditions, we start to sleep less in March. "If this springtime tiredness doesn't go away after one or two weeks, it could be a masked depression that becomes more apparent during this transition period," says Kasper. This is due to the fact that although dopamine is present, there is also a serotonin deficiency.

Tired of moving

"Most of them actually only suffer from spring fatigue for a few days. Your organism has a harder time with the adjustment than that of people who are not at all spring-tired," said the Viennese psychiatrist. Anyone who suffers from springtime tiredness every year should go outside as often as possible, especially towards the end of winter, even when the sky is overcast, and not too wrapped up in order to get the organism used to the change at an early stage. This has the extremely positive additional effect that vitamin D production in the skin is stimulated at an early stage. First on a smaller flame, then increasingly more. The immune system benefits from this and the susceptibility to infection is reduced. That is also good for the mood.

The good mood comes: when the sun is shining and the flowers are blooming, the serotonin and dopamine levels in the brain are readjusted. (Gerlinde Felix, April 24, 2018)