The brain consists of billions of nerve cells. In order for information to be processed and passed on in the brain, it needs certain messenger substances that communicate between the nerve cells. These so-called neurotransmitters work at the receptors (docking sites) of the nerve cells in the synapses (connection points between the nerve cells) and transmit stimuli to the next nerve cell by biochemical signal transmission [11, 15, 16].
Nowadays, the neurotransmitters serotonin, dopamine, and norepinephrine are thought to play an important role in the development and maintenance of depression. Studies indicate that the typical symptoms of depression are often associated with a dysbalance of these neurotransmitters, insofar as affected persons – compared to healthy persons – show a lower activity of these neurotransmitters. Antidepressants interfere with the neurotransmitters’ mode of action and help the brain to redress this imbalance, thus alleviating the symptoms of depression (e.g., brightening mood and normalizing drive). Not all antidepressants are effective in all patients and not all work in the same way . A distinction is made between newer and older antidepressants, which differ primarily in terms of their side effects and possible interactions with other drugs. Some antidepressants specifically target the release of serotonin (SSRIs) or norepinephrine (SNRIs), while others act more nonspecifically on multiple neurotransmitter systems (e.g., TCAs, MAOs). Due to their more severe side effects and rapid toxicity, older antidepressants are rarely prescribed nowadays .