Identifying the Mood-Regulating Neurotransmitter

Neurotransmitters are critical components of the brain's signaling system, each playing specific roles in regulating mood, cognition, and physical health. Among these neurotransmitters, dopamine is notably linked to the brain's reward system and is implicated in disorders such as schizophrenia and Parkinson's disease. Other neurotransmitters, such as serotonin and norepinephrine, also contribute to emotional regulation and arousal. Understanding the functions and interactions of these neurotransmitters can help elucidate their impact on behavior and mental health.

Which of the following neurotransmitters is primarily associated with the regulation of mood and social behavior, often referred to as the 'happiness neurotransmitter'?