The many rhythms observed at all levels of biological organization for the most part rely on a molecular or cellular mechanism: In this article I examine the mechanism of periodic processes that possess a psychological component. Three examples are considered in turn. The first pertains to bipolar disorders characterized by an oscillation between a manic state and a depressive state. The second is that of weight cycling, in which dieting is accompanied by periodic bouts of weight loss and regain. The third example relates to the oscillatory dynamics resulting from the interactions between members of a family system. A modeling approach suggests that beyond the differences in mechanism, all these periodic processes, which contain a psychological component, share common properties with biological rhythms.
Keywords: Oscillations; Models; Biological Rhythms; Bipolar Disorders; Weight Cycling; Instability; Bifurcations.