According to scientists, stress is the number 1 cause of mental and physical problems in humans in the 21st century. I think we are so stressed because life today is much more complicated than previously: there are too many options, too much stimulation and everything goes so fast. Way too fast.
If you go to the doctor because of your weight, he tells you to reduce your stress.
If you go to the doctor because you cannot get pregnant, he tells you to take care of your stress levels.
If you have a heart attack, your doctor tells you to work out your work-life balance to reduce your stress and tension.
If you have headaches, the doctors prescribes a vacation.
Conclusion: stress is caused by doctors!