Idiographic
Research at the level at which we also work: the patient before us.
The term idiographic is not new: it goes back to the German philosopher Wilhelm Windelband, who in 1894 set it against nomothetic. The tension it refers to is still with us.
Nomothetic research seeks general laws: what holds for people in general? This is the domain of randomised controlled trials, factor analyses on large samples and population parameters. Idiographic research studies the single case: one person, measured often, over time. This is the domain of case studies, n=1 designs and intensive longitudinal data.
In mental health care, the research of the past decades has been mainly nomothetic. That has yielded a great deal: we know which forms of treatment work on average, for which diagnoses and in which care pathways. In the consulting room, however, that average does not always say much about the person in front of us.
Two traditions, one application
It is increasingly recognised that we need both. Nomothetic research can supply hypotheses, and idiographic research can test them in the context of one particular life. A relation between sleep and mood that lies around .3 in group studies may be much stronger in an individual patient, but it may also be absent or even reversed. We only know once we measure it in her.
"The idiographic method shows what is connected in this one life, at this moment, and how that changes when something in the system shifts."
What does idiographic research look like?
There are several ways to work idiographically. The most accessible is ESM (Experience Sampling Method): a short questionnaire several times a day, over weeks or months. A few hundred measurements yield a time series in which it becomes visible how mood, behaviour, thoughts and context act upon one another in this one person.
Such data allow analyses that make little sense at the group level: vector autoregression (which variable predicts which other?), network analysis within the person, and the detection of early warning signals of relapse. For researchers and clinicians who would like to work with this, accessible R packages such as qgraph, mlVAR and esmpack are now available, which make it feasible even without a statistician of one's own.
What it does in the consulting room
The benefit for practice can lie at several levels. The clinician gains insight into what had until then been mainly an impression: does this patient feel worse after a bad night, or does the relation in her life run the other way? For the patient, the pattern of her own life becomes easier to read. And treatment can focus on what is connected in this person, rather than on what is connected on average.
In this sense idiographic work is not a step away from science, but rather science at the level at which we also act in the consulting room.