Your body has two mechanisms to deal with stress. For long-term/ongoing stresses (like an unstable relationship or chronic work stress), our bodies respond with a hormone called cortisol. For short-term/acute stress (like a big deadline, sudden conflict or threat to your physical safety), our body’s response is adrenaline.
Adrenal fatigue is caused by frequent adrenaline responses to acute stress. Too many ‘fight or flight’ responses without adequate time to recover lead to exhaustion of the glands and systems, which is what ‘adrenal fatigue’ refers to.
Modern life includes many more stressors than people once had, which is why we’re seeing an increase in this phenomenon.