Cycles and rhythms
Recurring patterns in time — from the sleep-wake regulation to the mood cycle.
Many processes that we as human beings harbour appear to run in rhythms. The twenty-four-hour sleep-wake cycle is perhaps the best known, but there are more: ultradian rhythms of an hour and a half, weekly rhythms, monthly rhythms, seasonal rhythms. On each of these scales, something seems to return.
The science that occupies itself with these rhythms is called chronobiology. For psychiatry this field has been relevant for some time: mood disorders often follow rhythms, and disruption of the sleep-wake cycle is one of the most robust correlates of depressive and bipolar complaints. But only with the rise of intensive longitudinal measurement (ESM, EMA) have we truly begun to see the rhythms of daily functioning more clearly.
What we see when we measure daily
When we ask a patient to fill in a brief questionnaire twice a day for several weeks, we frequently encounter a surprising structure. Mood has a daily curve that is characteristic for that person. Social contacts cluster around certain days. Sleep has a weekly rhythm linked to work and weekend. Complaints do not undulate at random — they have a dynamic.
Sometimes this dynamic is tight (a panic disorder that flares every Tuesday evening, a depression that worsens in January). Sometimes it is looser (a general pattern of decreasing energy as the week progresses). But rarely is it absent.
Cycles that drive each other
Many rhythms within a human being are coupled. Sleep and mood hang together. Eating rhythm and metabolism. Hormonal rhythm and menstruation. Social rhythm and sense of meaning. And all those rhythms are modulated from outside by work rhythms, school rhythms, annual rhythms, weather rhythms.
This seems to render psychiatric complaints, in a sense, ecological. A person with a fragile mood regulation depends on a whole ecology of rhythms that carry her. If one rhythm derails — a night shift, a broken relationship, a change of season — others may follow.
"The question is not whether a patient is depressed, but in which rhythm her depression moves." — freely after Wichers et al.
Implications for treatment
One who takes rhythms seriously may treat just a little differently. Sleep hygiene is no afterthought but foundation. Social-rhythm therapy (Frank, for bipolar disorder) is based on precisely this idea: stabilise rhythms and you stabilise the system. A good treatment shows the patient which rhythms carry her and which destabilise her.
Clinicians who work with ESM/EMA often get a different picture than a static interview yields. Not "how are you?", but "how have you been these past two weeks, at which moments, in which rhythms?"
A brief caution
Seeing a rhythm is easier than explaining a rhythm. What looks like a weekly pattern may be an artefact of when someone fills in her questionnaire. What looks like a seasonal effect may coincide with other things (winter busyness, holiday periods). To recognise true rhythms more is needed than a graph; we must know which patterns we can and cannot explain by the measurement structure itself.
The invitation that emerges, however, remains: would it be worth looking at your patient as someone who runs in time, and not only as someone in a state?