3 Clinical psychopharmacology3.3 Pharmacodynamics

3.3.3.4 The Cholinergic Adrenergic Balance Hypothesis mood

1 min read1 figure

Written by Resident Doctor Committee · Published

The hypothesis

Janowsky's 1972 hypothesis proposed that relative central cholinergic activity favours depression and relative adrenergic activity favours mania.

  • The model concerned a central balance, not an absolute deficit of one transmitter or peripheral autonomic activity.

  • Raised acetylcholine, reduced noradrenaline or both could tip the balance towards depression.

Pole

Proposed state

Cholinergic predominance

Low mood, reduced drive, psychomotor slowing

Adrenergic predominance

Activation, elevated or irritable mood, more goal-directed behaviour

Pharmacological evidence

Drug-induced mood-like states were the main evidence.

  • Intravenous physostigmine crosses the blood-brain barrier and inhibits cholinesterase, and early experiments showed brief falls in manic behaviour with more slowing or depressed affect.

  • Its nausea, bradycardia and sedation could lower mania ratings without treating the cause.

  • Antimuscarinic drugs can cause activation or euphoria, but also amnesia and delirium.

  • Stimulants may precipitate mania, and reserpine's depressive effects were inconsistent.

Sleep and arousal

  • Locus coeruleus noradrenaline supports vigilance, while basal forebrain and brainstem acetylcholine support attention, activation and sleep.

  • In classic rapid eye movement (REM) sleep models, acetylcholine is active and noradrenergic firing falls.

  • Some depressed groups show shortened REM latency and increased REM density.

  • Some challenge studies found greater REM latency responses in depressed patients or their relatives, which suggests a sensitivity difference rather than a mood mechanism.

Compare the cholinergic basal forebrain and pedunculopontine and laterodorsal tegmental nuclei with the noradrenergic locus coeruleus: both systems project to the cortex and support arousal, the two sides of the proposed balance. Drawn for MRCPsychiatrist

Why the model fails

  • Effects vary by receptor, circuit and state, and both systems can support attention.

  • Drug challenges produce brief, partial states with non-specific effects.

  • Agitated depression, dysphoric mania and mixed states challenge a single-axis model.

  • Peripheral autonomic measures poorly reflect central balance and are confounded by illness, anxiety and medication.

  • Stress, circadian, plasticity and other transmitter pathways also contribute.

Modern accounts focus on interacting networks: the ratio is not an established explanation of depression or mania.

Revision material for the MRCPsych examinations. Not clinical guidance, and not for use in patient care.