At the University of Oxford, Foster studies circadian rhythms — the internal 24-hour clocks that govern when we sleep, and that are partially regulated by exposure to light. According to his recent research, abnormal circadian rhythms are likely related to mental illness. Foster and his colleagues have found that patients with a range of afflictions — from schizophrenia to bipolar disorder — show severely disrupted sleep cycles. The work may have implications for diagnosing mental illness; certain sleep patterns may help pinpoint a disorder. The work could also eventually lead to new treatments for mental illness through tweaking sleep patterns with light therapy.