Vitamin B6 has been known to reduce blood estrogen and increases  progesterone. Therefore, B6  deficiency will cause decreased liver metabolism of estrogen, causing an excess of estrogen, this results in "estrogen dominance."

Estrogen imbalance effects mood swings by increasing the activity of the biogenic amines, epinephrine, norepinephrine, and serotonin levels, which affect moods. Epinephrine triggers anxiety. Norepinephrine causes hostility and irritability. Serotonin at high levels creates nervous tension, and inability to concentrate.

Dopamine, produced by the brain, balances out the effects of the biogenic amines by inducing relaxation, increases mental alertness, and works to prevent sodium and water retention.

Without sufficient dopamine, the biogenic amines are not held in check, moods are greatly affected in a negative manner, and sodium and water retention increase.

Estrogen also increases the level of the adrenal hormone aldosterone, which prevents the normal excretion of salt from the kidneys, adding to fluid retention. This creates edema-like symptoms of bloating, abdominal swelling, and swollen breasts.

Excess fluid swells the nerve tissue and membranes surrounding the brain. The brain is encased within the skull, and can only expand as far as the skull permits. This leads to torturous migraine headaches that are often described as "vise-like."