Disruption or disorganization of biological rhythm is observed in

Disturbance of biological functions is common with depression, with insomnia (or sometimes increased sleep), loss of appetite and weight (or sometimes hyperphagia and weight gain), and loss of sexual drive. When the disturbance is severe, it is called as melancholia ( somatic syndrome) The somatic syndrome in depression is characterised by: a. A significant decrease in appetite or weight b. Early morning awakening, at least 2 (or more) hours before the usual time of awakening c. Diurnal variation, with depression being worst in the morning d. Pervasive loss of interest and loss of reactivity to pleasurable stimuli e. Psychomotor agitation or retardation. Ref: A Sho Textbook of Psychiatry, Niraj Ahuja, 7th Edition, pg. no.72