Cycles and rhythms
Recurring patterns in time, from the sleep-wake rhythm to the mood cycle.
Many processes that take place within us seem to run in rhythms. The twenty-four-hour sleep-wake rhythm is probably the best known, but there are others: ultradian rhythms of about an hour and a half, and weekly, monthly and seasonal rhythms. On each of these time scales something seems to recur.
The science concerned with these rhythms is called chronobiology. For psychiatry this field has been relevant for quite some time: mood disorders often follow a rhythm, and a disturbed sleep-wake cycle is among the most robust correlates of depressive and bipolar complaints. Only since the rise of intensive longitudinal measurement (ESM, EMA), however, have we been able to see the rhythms of daily functioning clearly as well.
What we see when we measure daily
When we ask a patient to fill in a short questionnaire twice a day for a few weeks, a surprising structure not infrequently emerges. Mood has a daily course that is characteristic of the person. Social contacts cluster around certain days. Sleep has a weekly rhythm linked to work and weekends. Complaints do not rise and fall at random but follow a dynamic of their own.
Sometimes that dynamic is tight, as in a panic disorder that flares up every Tuesday evening or a depression that worsens in January. Sometimes it is looser, such as a general pattern of declining energy as the week goes on. But it is seldom entirely absent.
Cycles that drive each other
Many rhythms in a person are coupled to one another: sleep and mood, eating rhythm and metabolism, hormonal rhythm and menstruation, social rhythm and the sense of meaning. All these rhythms are, moreover, influenced from outside, by the rhythm of work and school, of the year and of the weather.
This seems to make psychiatric complaints, in a certain sense, ecological. Someone with vulnerable mood regulation depends on a whole ensemble of rhythms that carry her. If one rhythm becomes disrupted, for example by a night shift, the end of a relationship or the change of season, other rhythms may follow.
"The question is not whether a patient is depressed, but with which rhythm her depression moves." (freely after Wichers et al.)
Implications for treatment
Taking rhythms seriously may lead to treating somewhat differently. Sleep hygiene then becomes not a finishing touch but a foundation. Frank's social rhythm therapy for bipolar disorder rests on precisely this idea: stabilising rhythms also stabilises the system. A good treatment can help the patient see which rhythms carry her and which throw her off balance.
Clinicians who work with ESM or EMA often obtain a different picture from the one a single interview provides. The question then shifts from "how are you?" to "how have the past two weeks been, at which moments and in which rhythms?"
A caveat
Seeing a rhythm is easier than explaining it. What looks like a weekly pattern may be an artefact of the moments at which someone fills in the questionnaire. What seems to be a seasonal effect may coincide with other factors, such as winter busyness or holiday periods. Recognising genuine rhythms takes more than a graph: we need to know which patterns can already be explained by the measurement design itself.
The invitation that this perspective offers nonetheless stands: it seems worthwhile to us to see a patient as someone who moves through time, and not only as someone who is in a particular state.