Methods of Assessing Circadian Rhythms in Animal Models of Affective Disorders

The existence of circadian rhythms, near 24-hour patterns of variation in biological functions, has been well established in many species. There is currently a great deal of interest in whether or not disturbed circadian rhythms are involved in the pathogenesis or etiology of some types of psychiatric disorders. Indeed, several types of sleep disorders, such as delayed sleep phase syndrome (Weitzman et al., 1981; Czeisler et al., 1981), advanced sleep phase syndrome (Moldofsky et al., 1986), non-24-hour sleep-wake syndrome (Miles et al., 1977; Kokkoris et al., 1978; Weber et al., 1980), and narcolepsy (Moskoetal., 1983), are considered to be diseases based on disturbed circadian rhythms.