Drinking too much coffee for a long period of time can cause a person to feel sleepy because the adrenal glands become exhausted, according to Natural News. Constant consumption of coffee puts the body in fight-or-flight mode, and when the stimulation of adrenal glands wears out, a person can be left fatigued. Anxiety, mood swings, depression, irritability, sleep disturbance, headaches or confusion are also possible.
When a person consumes coffee, the caffeine triggers unregulated neuron firing in the brain. This activity triggers the pituitary glad to produce hormones that stimulate the adrenal gland, which in turn produces adrenaline, according to Natural News. Adrenaline gives an energy boost initially. In order to combat the fatigue that is the result of adrenaline levels dropping, a person may consume more coffee in order to fight fatigue. This puts a lot of stress on the body and brain. Natural News suggests that after a long period of time of drinking too much coffee it takes much more coffee to receive an energy burst from adrenaline production. This is known as adrenaline depletion. Like any other form of drug abuse, drinking too much caffeine results in the person building up a tolerance to it. If the person tries to wean himself off caffeine, he experiences withdrawal symptoms, according to Natural News.