Medical research on the effects of excessive light on the human body suggests that a variety of adverse health effects may be caused by light pollution or excessive light exposure, and some lighting design textbooks[33] use human health as an explicit criterion for proper interior lighting. Health effects of over-illumination or improper spectral composition of light may include: increased headache incidence, worker fatigue, medically defined stress, decrease in sexual function and increase in anxiety.[34][35][36][37] Likewise, animal models have been studied demonstrating unavoidable light to produce adverse effect on mood and anxiety.[38] For those who need to be awake at night, light at night also has an acute effect on alertness and mood.[39]
Context:
Two friends, John and Abe, worked at the same warehouse. John was exposed to very strong light all the time, while Abe worked in a  more normal environment. John started experiencing health problems after a while.
Q: Which worker experienced weaker effects on alertness and mood, John or Abe?