Neurotransmitters

Serotonin

Function: mood, sleep appetite
Too little: depression anxiety
Too much: serotonin syndrome

Norepinephrine

Function: Alertness, focus, energy
Too little: depression, poor concentration
Too much: anxiety, hyperarousal

Dopamine

Function: Reward, motivation, movement
Too little: depression, apathy
Too much: Psychosis, hallucinations

GABA

Function: calming, inhibitory neurotransmitter
Too little: Anxiety, panic
Too much: Sedation

Glutamate

Function: excitatory neurotransmitter
Too little: cognitive deficits
Too much: cholinergic effects

Acetylcholine

Function: Memory and learning
Too little: cognitive deficits
Too much: Cholinergic effects

Histamine

function: wakefulness, gastric secretions, cardiac stimulations
Too little: sedation
Too much: Insomnia