Dopamine: Deficiencies make you crave alcohol, illicit drugs, opiate painkillers and cigarettes. Yes, correcting dopamine levels can help addiction. But too much dopamine is associated with aggression and paranoia. Imbalances with this neurotransmitter (especially when low) are tied to Parkinson's, depression, attention/focus problems, schizophrenia, spectrum disorders and autism.
Histamine: It makes you sneeze, but did you know that chronically high levels are tied to migraines and eczema, and obsessive compulsive behavior? Low levels cause fatigue, low libido and paranoia.
Serotonin: Popular antidepressants lift it temporarily including the Zoloft you take. Deficiencies can cause fatigue, muscle cramps, irritability and always feeling hot. High serotonin is tied to bone loss, irritable bowels, trembling, nausea, and a feeling of overconfidence that some might call arrogance.
If you're lacking norepinephrine you'll have profound adrenal fatigue and stubborn weight gain. You'll want energy shots all day long. If you're GABA-deficient (gamma-aminobutyric acid), insomnia and anxiety are evident to those around you. High epinephrine and you're too aggressive.