Like all the B Vitamins, Vitamin B6 is an important "co-factor", and is important to the functioning of more than 60 ENZYMES that effect crucial body processes. In addition, Vitamin B6 is also easily depleted and even more so when the body experiences stress.
A deficiency in Vitamin B6 may increase duration and/or intensity of Pre-Menstrual Syndrome (PMS), it can aggravate or lead to mood disorders, irritability, depression and drowsiness.
Now you may ask, "WHY is B6 linked so much to our moods?" The reason: Vitamin B6 aids the amino acid, L-tryptophan, in its synthesis of serotonin.