Which neurotransmitter is most associated with feelings of well-being and mental alertness?

The correct choice, serotonin, plays a crucial role in regulating mood, anxiety, and overall feelings of well-being. It is often referred to as the "feel-good" neurotransmitter because of its significant impact on happiness and emotional stability. Higher levels of serotonin are generally associated with improved mood and a greater sense of contentment, while lower levels have been linked to depressive symptoms and anxiety disorders.

Additionally, serotonin contributes to cognitive functions, including memory and learning, which can enhance mental alertness. Its influence is a fundamental reason why many antidepressants target the serotonin system, as increasing serotonin availability can lead to improved mood and mental clarity.

In contrast, while dopamine is also involved in mood and reward processing, its primary association is with pleasure and motivation rather than just general well-being. Norepinephrine is primarily involved in the body's response to stress and arousal, and GABA serves as a major inhibitory neurotransmitter that helps regulate anxiety and induces calmness, but it does not directly promote feelings of joy or alertness in the same way serotonin does. Thus, serotonin stands out as the neurotransmitter most closely connected to feelings of well-being and mental alertness.