A well-known practical problem and an important categorisation
If you regularly work with Biofeedback you probably know this situation well:
The electrodes are correctly positioned, the setting is calm, the client appears attentive - and yet the skin conductance remains flat or cannot be measured at all.
This can be unsettling, especially at the beginning of biofeedback work:
Have I connected something incorrectly? Is the sensor defective? Is the client „not co-operating properly“?
What is often overlooked: Science has not yet provided a clear figure on how often a skin conductance value cannot be measured in the general population.
The psychophysiological literature describes a strong inter-individual variability of skin conductance with sometimes very low or absent signals, However, valid epidemiological prevalence data on so-called skin conductance „non-responders“ are still lacking.
From my own therapeutic practice, I know how often this issue nevertheless arises in everyday life - and how relieving it can be for both therapists and clients to understand:
In most cases, an unmeasurable skin conductance is not a measurement error or a „failure“ of the method, but an expression of physiological, medical, psychological or situational characteristics.
With this article, I would like to give you sound, practical guidance on how to remain calm, competent and flexible in precisely these situations - and continue to use biofeedback sensibly and effectively.
Briefly explained:
A skin conductance value cannot be measured if the sweat gland activity is very low, medication is active, the autonomic nervous system is less reactive or technical factors impair the measurement.
Physiological causes
Very low sweat gland activity
The skin conductance is based on the activity of the eccrine sweat glands. In some people this is naturally very low.
Typical backgrounds:
- constitutionally low sweat secretion
- More common in older people
- Genetic differences in autonomic reactivity
Even if the measurement is correct, there are hardly any changes in skin conductance.
Strong parasympathetic basic regulation
Some clients have a very low sympathetic tone, in particular:
- Strongly controlled, performance-orientated personalities
- People with high cognitive control
Features:
- hardly any phasic EDA reactions
- Subjectively perceived activation without measurable change in skin conductance
The body reacts in a regulated way, not „underactivated“.
Cold hands with poor circulation
A very common practical factor.
Possible causes:
- peripheral vasoconstriction
- Stress or anxiety
- Raynaud's phenomenon
Consequence:
- Reduced sweat secretion
- Skin conductance barely measurable or not measurable
Medical causes
Neurological diseases
Disorders of the autonomic nervous system have a direct effect on skin conductance.
Relevant are among others:
- Parkinson's disease (autonomic dysfunction common)
- Polyneuropathies (e.g. diabetic)
- Small fibre neuropathies
- Lesions of autonomic nerve tracts
Dermatological factors
The skin itself also plays a central role.
Possible restrictions:
- Very dry, keratinised skin (hyperkeratosis)
- Scar tissue at the measuring points
- Chronic skin diseases (e.g. eczema)
The electrical conductivity is significantly reduced.
Endocrinological factors
Particularly relevant, but often overlooked:
- Hypothyroidism (underactive thyroid gland)
→ Low metabolism, reduced sweat activity - Dehydration
→ too little liquid, lots of coffee, alcohol the day before - Overall low general metabolism
Drug influences
Medication with an anticholinergic effect
These directly inhibit sweat gland activity.
Examples:
- tricyclic antidepressants
- Antipsychotics with an anticholinergic profile
- certain antiparkinsonian drugs
Sympathetic depressant medication
These also significantly reduce skin conductance reactions, e.g:
- Beta blockers
- Sedatives / benzodiazepines
- Opioids
Result: greatly reduced or cancelled skin conductance.
Technical and measurement-related causes
Electrodes and sensors
- Insufficient skin contact
- Sensor defective
→ Easy to check: if the sensor reacts on another person, then the sensor is OK
Unsuitable measuring location
- Finger backs instead of finger berries
- Areas with low sweat gland density
→ try another finger
Artefacts
- Movement
- Pressure on the electrodes
- Electrical interference in the room
Situational and psychological factors
Lack of emotional activation
- neutral contents
- No emotionally relevant stimuli
- Strong cognitive control
Habituation
- Attenuated reactions with repeated measurement
- especially for experienced biofeedback clients
Dissociation or emotional flattening
- Trauma-related disorders
- depressive states with anhedonia
Subjective experience and physiological reaction can be strongly decoupled.
Environmental conditions
- Low room temperature
- Dry indoor air
- Cold acclimatisation before the session
Clinical-practical tips for everyday life
- Don't panic: A skin conductance that cannot be measured does not mean that you are doing something wrong.
- Change parameters:
- Finger temperature
- HRV / Breathing feedback
- EMG
- Warm up your hands, then measure again
- Actively request medication
- Document the time of measurement and room climate
- Focus on Self-awareness and regulation, not on perfect curves
Conclusion: Biofeedback creates clarity and new opportunities
Skin conductance is a valuable biofeedback parameter, but it cannot be measured equally well for every person and at every point in time.
A differentiated understanding of the possible causes helps, remain confident, work flexibly and accompany clients competently.
Biofeedback does not live from individual numbers, but from Understanding, context and therapeutic relationship.
Thank you for the valuable information; very helpful.
Thank you very much for the comprehensive explanations!