Asked by: AnonymousCaffeine is a powerful central nervous system stimulant. After too much caffeine serotonin levels can fall, leading to a ‘crash’. This can cause anxiety, depression and poor concentration. Caffeine also stimulates adrenaline from the adrenal glands that makes the liver release glycogen, raising blood sugar levels and temporarily giving you more energy. The pancreas then releases insulin to deal with the excess sugar and when levels drop again, you feel lethargic and ‘wiped out’. Excessive caffeine use can harm both the adrenals and pancreas, and the ‘wiped-out’ feeling can become more serious. Although very widely used, caffeine is an addictive psychoactive drug.