Feedback (feedback loops)
The mechanism that can drive addiction as well as recovery, and everything in between.
Feedback, or coupling, is in our view among the most universal mechanisms in complex systems. It is what can turn a straight line into a spiral.
The basic idea is simple: the result of a process influences the process itself. If the outcome amplifies the process, we speak of positive feedback: a snowball that grows as it rolls, a rumour that spreads, a panic attack that feeds itself. If the outcome dampens the process, we speak of negative feedback: the thermostat in the living room, insulin production after a meal, the automatic correction on a bicycle leaning too far to the left.
Positive feedback is not positive
The terminology can mislead. Positive feedback does not mean "good", but "amplifying". A vicious circle is positive feedback: sleep problems lead to fatigue, fatigue to rumination, and rumination back to sleep problems. The system amplifies itself and the downward spiral continues. The same mechanism also drives upward spirals: self-confidence leads to daring, daring to new experiences, and experiences back to self-confidence. In both cases it is a matter of positive feedback; the mechanism is the same, only the direction differs.
"Vicious circles and upward spirals follow the same law. The only question is which way the system rolls."
Negative feedback keeps systems stable. It is the reason we do not simply remain feverish, do not forget to breathe and do not just fall off a chair. But negative feedback can also hold a system captive: a system that is "corrected" so strongly that it can hardly set itself in motion, choose or change any more.
Feedback in the consulting room
For mental health care, feedback matters in three ways. Clinically: much psychopathology can be understood as a feedback system. Depression as a downward spiral of inactivity and mood, anxiety as positive feedback between avoidance and threat perception, eating disorders as coupling between body, control and emotion. Describing a problem in terms of feedback often makes it quicker to see which links keep it going.
Therapeutically: many interventions can be seen as attempts to break or redirect a feedback loop. Cognitive restructuring acts on the coupling between thought and feeling, behavioural activation on that between inactivity and mood, exposure on that between avoidance and anxiety. It is probably no coincidence that so many active elements of psychotherapy can be described as feedback interventions.
Methodologically: feedback makes psychological data difficult to interpret. If A and B mutually amplify each other, what is cause and what is effect? In a linear model this can hardly be resolved. In a dynamical systems model, with time series, vector autoregression or network analysis, the question does become answerable: we see over time which variable predicts which other.
What thinking in feedback does
What stands out time and again in thinking in terms of feedback is how self-evident it feels once it has been seen. Patients often recognise it straight away, because they experience it every day. For clinicians it takes more effort: deliberately looking for the feedback structures, and designing interventions that act on the loop and not only on the symptom. That is what process-based therapy aims at: moving from combating symptoms to recognising and influencing the active feedback mechanisms.