What is the primary role of serotonin in mental health?

The primary role of serotonin in mental health is to regulate moods and emotions. Serotonin is a neurotransmitter that plays a crucial part in influencing emotional states, anxiety levels, and overall mood. Its balanced levels are associated with feelings of well-being and happiness. When serotonin levels are imbalanced, it can lead to various mental health issues, such as depression and anxiety disorders.

In contrast, while cognitive function, motor functions, and immune responses are important aspects of overall health, they are not the primary focus of serotonin's role in mental health. Enhancements in cognitive function are more associated with other neurotransmitters like dopamine and norepinephrine. Motor functions are primarily controlled by neurotransmitters such as acetylcholine. Immune responses involve a different set of biochemical mediators and are not significantly regulated by serotonin in the context of mental health. Thus, the role of serotonin is distinctly linked to mood regulation, making it the correct choice in this context.