Experiments on mice have shown that throwing off their ancient circadian rhythms by artificially altering the length of their days has a substantial impact on their bodies and brains. This suggests that the modern, round-the-clock lifestyle, made possible by electric lighting, could disrupt metabolism and interfere with learning in ways that are only just beginning to be understood.
Researchers put mice through 10 weeks in 20-hour light-dark cycles, instead of their natural 24-hour circadian cycle. After six weeks, the mice got fatter, showed less mental flexibility and were more impulsive.
Science Daily reports:
"The researchers believe that [the effects of an altered circadian cycle] may affect how an individual, whether animal or human, responds to additional challenges to the immune or metabolic systems, such as infection ... They are also working on models to understand the impact of different kinds of light-dark shifting such as those experienced by flight crews, shift workers, military personnel and medical residents."