资料：It's so common to hear people say， “I’m stressed out，” almost as a badge of honor， as if this is a symptom only of our fast-paced modern life. But in her book， “Exhaustion： A History，”Anna Katharina Schaffner writes that the syndrome of mental exhaustion has existed almost since the beginning of human history.
Commentators claim [ ours] is the most exhausting period in history， the demands on our energy reserves being unprecedented. By implication， they represent the past as a less energy-draining time in which people lived much less stressful lives in harmony with nature and the seasons，“says Schaffner， a. professor of comparative literature and medical humanities at the University of Kent in England， in an email interview. I asked myself whether that was really the case， and started researching other historical periods in search of earlier discourses on exhaustion. To my surprise， I found that ours is far from being the only age to have perceived itself as the most exhausted-this is in fact a perception shared by many historical periods， albeit in different ways and for different reasons.”
Schaffner found information about exhaustion going all the wy back to antiquity. This is not the same thing as physical exhaustion —certainly most， people in earlier times had life physically harder—but concurrently throughout history was this idea of being mentally exhausted， what we might call today being “stressed”or “burned out.”
In the past， she says， the condition went by many names： melancholia， depression， chronic fatigue syndrome or acedia， “a theological version of melancholia， also described as weariness of the heart.”and popular in Medieval times. Causes ranged from physical ailments and chemical imbalances in the brain to spiritual failings or even the alignments of the planets， Often there was a different explanation for each historical period.
“In the late 19th century， for example，. a faster pace of life as a result of trains， steam boats， electricity， and telegraphy was held responsible for the sudden explosion in the number of cases of what was diagnosed as neurasthenia-this diagnosis being structured around a deficiency in nerve force， and manifesting itself in weakness， lethargy. hopelessness， and various other symptoms.”she says.
Other mental ailments throughout time were attlbuted to “the availability of exotic food and spices in the 18th century the education of women in the 19th century，. or the new psycho-social pressures of neo-liberal capitalism in our own time”she adds
So if exhaustion has been with us forever， what does that mean for we moderns? “An historical perspective can help to counter the sense that our way of life is more detrimental to human wellbeing than those in the past， and to make us feel less alone，” says Schaffner. “Of course， this historical perspective also challenges the idea that current states of exhaustion are a unique badge of honor. Thus historicizing exhaustion can， on the one hand， reassure us and， on the other hand， challenge the narratives on which we rely to give our suffering aspecial value.”

Based on commentators views in Para.2， mental exhaustion may be caused by ______

A.the fast-paced modern life.
B.the significant events in human history.
C.increasing consumption of the energy reserves.
D.less harmonious life with nature and the seasons.