Entropy
From thermodynamics to therapy: how a physics concept speaks of rigidity.
Entropy is, to our minds, one of the most beautiful concepts in physics, and at the same time one of the most confusedly applied. Broadly speaking, it refers to the degree of unpredictability or disorder in a system.
In thermodynamics, entropy is the measure of how many microscopically different states a system can occupy, given what we observe macroscopically. A cup of scalding hot coffee and a cup of ice-cold coffee differ enormously at the macro level — but the hot coffee has many more microscopic configurations corresponding to that same temperature. High entropy means: many possibilities, much movement, little structure.
The second law and the direction of time
The second law of thermodynamics says that the entropy of a closed system always increases. A student's room becomes messy on its own, not tidy on its own. A cup of coffee cools. Ice cubes melt. Entropy grows.
What makes it, then, that in an open system (a living being, an ecosystem, a person) we nevertheless see ordered structures? The answer is that open systems take in energy from outside — food, sunlight, warmth — and may thus locally lower entropy, at the cost of an entropy increase elsewhere. Living systems "fight" against the second law, as Ilya Prigogine put it, and the effort that costs is precisely what we call life.
Entropy in psychological time series
The application to psychological data is a particular one. There we often use sample entropy or permutation entropy: measures of how predictable a time series is. A patient whose mood follows exactly the same course every day has low entropy in her mood. A patient who shows different patterns every day has high entropy.
"In clinical practice, both too much and too little entropy seem problematic. Too much: chaos and instability. Too little: rigidity and locked patterns."
This is an important nuance. A healthy system has moderate entropy — enough variation to adapt to changing conditions, enough stability to remain recognisably itself. Too little entropy we see in depression (everything feels the same, behaviour rusted in place), in obsessive patterns, in some forms of trauma. Too much entropy we see in some forms of anxiety, in dissociation, in acute crises.
What this means in practice
The usefulness of entropy as a concept does not lie in precise measurement (that is methodologically difficult), but in the way it shapes our looking. A patient who says "it is always the same" describes a system of too low an entropy. A patient who does not know who she will be tomorrow describes a system of too high an entropy. In both cases, restoring a healthy moderate entropy — flexible, but not rudderless — is a worthy aim.
Schiepek has integrated entropy measures as one of the indicators in his Synergetic Navigation System. A marked drop in entropy may, in his work, be an early warning signal of an approaching phase transition in the therapeutic process — sometimes for the better, sometimes for the worse.