Which of the following neurotransmitters is primarily concerned with regulating the mood and emotional states, including anxiety?

The neurotransmitter that is primarily concerned with regulating mood and emotional states, including anxiety, is serotonin. Serotonin plays a crucial role in the brain's ability to modulate mood, anxiety, and overall emotional well-being. It is often referred to as the "feel-good" neurotransmitter due to its influence on feelings of happiness and satisfaction. Low levels of serotonin are commonly linked to mood disorders such as depression and anxiety, highlighting its importance in emotional regulation.

While the other neurotransmitters listed—dopamine, norepinephrine, and GABA—also have roles in mood and emotional states, their functions are not as directly associated with anxiety management as serotonin. Dopamine primarily regulates pleasure and reward, norepinephrine is involved in arousal and alertness, and GABA serves as an inhibitory neurotransmitter that helps to calm neural activity. These functions can influence mood and anxiety, but serotonin is specifically recognized for its pivotal role in emotional stability and response to anxiety.