The Neuroscience of Anxiety: The Role of Serotonin in Emotional Regulation

Researcher's Chronicle | Ana Rita Costa is a postdoctoral researcher in the field of neuroscience at the Department of Biochemistry and Biophysics of Stockholm University and at SciLifeLab. Her research focuses on understanding how serotonin-producing neurons are involved in anxiety processing. In this article, she explores how much we still don’t know about how the brain processes anxiety and how this limited knowledge hinders the development of more effective treatments.

Anxiety is one of the most common mental disorders, affecting around 310 million people worldwide—approximately 4% of the global population. While treatments for anxiety are available, their effectiveness is still limited and often insufficient for many individuals.

In certain contexts, feeling anxious is normal and, to some extent, necessary. When not pathological, anxiety plays a crucial role in our survival, helping us identify dangers and prepare for the unknown. It acts as a driver that promotes or inhibits exploration and regulates adaptation to new challenges.

In certain contexts, feeling anxious is normal and, to some extent, necessary. When not pathological, anxiety plays a crucial role in our survival, helping us identify dangers and prepare for the unknown. It acts as a driver that promotes or inhibits exploration and regulates adaptation to new challenges.

Understanding how our brain processes the anxiety–exploration dynamic is essential—not only to uncover the mechanisms that govern behavior but also to develop more effective strategies for treating and preventing related disorders.

One neurotransmitter that plays a central role in this process is serotonin. This neurotransmitter is synthesized by a specific group of neurons located in the brainstem, known as the raphe nuclei. These neurons are involved in a wide range of functions, from basic homeostatic regulation to the modulation of psychiatric and mood disorders.

The connection between serotonin and anxiety is supported by scientific evidence, particularly from the pharmacological effects of serotonin reuptake inhibitors—one of the most frequently prescribed classes of medications for treating depression, but also widely used for anxiety. Despite their widespread use, these drugs show limited efficacy, and the mechanisms by which the brain—especially serotonin-producing neurons—influences these processes remain poorly understood.

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The main goal of this project is to thoroughly investigate how, in a healthy brain, serotonin-producing neurons and the information they transmit to different brain areas are involved in anxiety processing, through the manipulation and monitoring of neuronal activity. By studying the behavior of these neurons under normal conditions, it is possible to identify the neuronal mechanisms that regulate anxiety management and reveal how this regulation may be disrupted in psychiatric disorders where serotonin processing is altered. A deeper understanding of these processes will not only shed light on the mechanisms underlying anxiety but also pave the way for developing more effective therapies.

References:

Institute for Health Metrics and Evaluation (IHME). GBD Results Tool. Global Health Data Exchange. Seattle: Institute for Health Metrics and Evaluation, 2019.

Bateson, M., Brilot, B., & Nettle, D. (2011). Anxiety: an evolutionary approach. The Canadian Journal of Psychiatry, 56(12), 707-715.

Ligneul, R., & Mainen, Z. F. (2023). Serotonin. Current Biology, 33(23), R1216-R1221.

Jakubovski, E., Johnson, J. A., Nasir, M., Müller‐Vahl, K., & Bloch, M. H. (2019). Systematic review and meta‐analysis: Dose–response curve of SSRIs and SNRIs in anxiety disorders. Depression and anxiety, 36(3), 198-212.

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