Some researchers believe that the incandescent light bulb may be ultimately responsible for a variety of illnesses.
Permanent Jet Lag
Organisms evolved to adjust themselves to predictable patterns of light and darkness, in a physiological cycle known as the circadian rhythm. Once artificial light effectively varied the length of a day, the average night's sleep decreased from around nine consistent hours to roughly seven, varying from one night to the next.
The irregularity prevents circadian rhythms from adjusting to a pattern, and creates a state of permanent "jet lag."
Ulcers, Heart Disease, CancerThis could make people more susceptible to a variety of health problems, since it activates the stress response and weakens the immune system. Irregular sleep cycles can lead to stress, constipation, stomach ulcers, depression, heart disease, and even cancer.