Theory 18/Life, Medicine & Mind /Psychiatry
Depression Is a Coupling Threshold
Depression is explained by a chemical deficit. The persistence may be a property of the network.
Depression is a network state that becomes self-sustaining when coupling between mood-related regions exceeds a threshold, so treatment response depends on reducing coupling rather than on raising a neurotransmitter.
01The evidence
Neuroimaging shows altered connectivity in depression, and the alterations normalise with successful treatment regardless of modality.
02The tension
Monoamine models predict response from transmitter levels and explain neither the delay in response nor the similar efficacy of mechanistically different treatments.
03The mechanism
A network with strong recurrent coupling can maintain a state without external input. Below a threshold, mood returns to baseline after a perturbation; above it, the state persists.
That makes coupling the determinant, and predicts that treatments which reduce it should work regardless of their primary target.
04What this is not
Those models target transmitter levels. This targets coupling, which explains delayed and modality-independent response.
05Predictions
- P1Persistence should track coupling strength.
- P2Coupling reduction should predict response.
- P3Different modalities should converge on coupling.
06Refutation
Response tracking transmitter change rather than coupling would favour the deficit model.
07What it changes
It would change how treatment response is monitored.