Adrenal gland.. Mostly relies on good neurochemistry, which relies on 2 things: good diet, and good gut health. Meaning: eat your yogurt (and bio flora for your tummy) and get all your amino acids! Good gut health = great digestion -> what you eat becomes good neurochem -> happiness and clarity.
Can you provide the source for this? I would like to read up.
Any other sources of knowledge to learn about neurosciences you would like to recommend would also be helpful.
There being no concise source on the matter of general health, diet, good neurochemistry, and mood, I can but offer a collection of disparate books:
Principles of Neuroscience (Kandel, Schwartz, Jessell) is a great textbook.
Emotional Intelligence (Bradberry)
Zen Mind, Beginner's Mind (Suzuki Roshi)
I also read a lot of personal experience vault essays on erowid.org (regarding "experimental medicine," for lack of better terminology)