How can an imbalance of brain neurotransmitters cause delusions, insanity, etc?

Unknown for sure: There is a great deal of research in neurobiology about how the neurotransmitters' changes translate in the brain into thoughts and feelings, normal or abnormal. There are theories but no consensus yet. Perhaps my colleagues could add their views. But clinically, these connections have been clearly observed and symptoms like delusions can vastly improve with medications working at this level.