What Is Nervous System Lability?

Why does one person remain calm and reasonable in a critical (conflict or simply unusual) situation, while another reacts with excessive agitation or aggression? It turns out that not everything can be explained by personality type, character accentuation, or upbringing. In psychology and physiology, there is a concept called lability—and it largely determines how people behave and feel in circumstances that differ from the norm.

In general, lability means mobility, instability, variability, or flexibility. The term was introduced in 1886 by N.E. Vvedensky, a Russian physiologist and student of Sechenov. It reflects several characteristics of the nervous system:

• The speed at which an excitatory impulse arises
• The speed at which it reaches its target
• The speed of the inhibitory (braking) response
• The frequency of tissue stimulation in response to a nerve impulse
• The time it takes for tissue to recover after each excitation cycle

Many experts distinguish between lability in different fields. In psychology, mental lability is primarily mood instability, emotional hyperexcitability, and overly sharp or sometimes inadequate reactions to events. In physiology, it refers to dysfunction of the autonomic nervous system, where external triggers cause the body to malfunction.

Many scientists argue that lability should be considered equally in both psychology and physiology, as it reflects a borderline state between the two. Here’s an example to illustrate:

• Situation: A person unexpectedly learns they’ve been fired from a well-paid, beloved job they’ve held for many years.
• Normal nervous system: The person gets upset, tries to find out the reasons, draws conclusions for the future, and starts looking for a new job. Even if the firing was unfair and they feel hurt, they won’t cause a scene. Even a choleric person might say something sharp but nothing more. Explanation: Excitation and inhibition processes are balanced.
• High lability: Depending on their personality, the person may either break down in hysterics or start a scandal. They’ll also show symptoms of autonomic dysfunction: sweating, blood pressure spikes, rapid heartbeat, hand tremors. It’s obvious they can’t control themselves. Even though the episode passes quickly, it often leads to prolonged depression. Explanation: Excitation is too fast, and inhibition can’t keep up.
• Low lability: The person quietly collects their things and leaves without confrontation. This isn’t an act—they genuinely don’t care. Explanation: The excitatory impulse is too slow to trigger any response.

In such borderline cases, the second person is said to have a labile nervous system (reacts instantly, with slow inhibition), while the third has a rigid nervous system (doesn’t respond or resist stimuli).

Types of Lability

By Excitation Speed

• Low lability: Typical of a rigid nervous system, with minimal response to external stimuli.
• High lability: Instant response, with inhibitory factors (braking impulse, upbringing, personality type) failing to work.

By Manifestation

• Impulsive: Clearly expressed both psychologically and physiologically.
• Moderate (borderline): Can be relatively restrained depending on the situation.

By Severity

• Mild: Minor but noticeable behavioral deviations.
• Moderate: Both psychological and autonomic symptoms are diagnosed.
• Severe: Development of various complications.

By Area of Manifestation

• Emotional lability: Mental lability, characterized mainly by mood instability and overly intense reactions.
• Autonomic lability: Physiological lability, where bodily system malfunctions come to the forefront.

These two types rarely exist in pure form; their symptoms often overlap, leading to diagnoses recognized in the ICD-10. Organic emotionally labile asthenic disorder (simply “labile disorder”) is treated by psychiatrists, psychotherapists, and neurologists.

Specific Types of Lability

Type 1: Intellectual Lability

Intellectual lability is considered a positive trait of the nervous system. Here, a high speed of excitation works in a person’s favor: they react instantly to tasks, solve them quickly and accurately, and immediately switch to the next one. This multitasking ability is highly valued in today’s fast-paced world—sometimes even more than IQ.

Example: A person with high intellectual lability rides the subway in the morning. It may seem like they’re not doing anything special, but in reality, they are:

• Watching the train’s movement to avoid missing their stop and assessing their surroundings (when to stand up, offer a seat, etc.)
• Listening to music
• Mentally planning their day: prioritizing work tasks and deciding what can wait
• Scrolling through social media feeds to stay updated
• Chatting with several people in different messengers

And all of this at once!

Type 2: Social Lability

This type is not well described, and psychologists have differing opinions. Some believe it’s a result of emotional instability, making it hard for socially labile people to form strong, lasting relationships, as not everyone can handle their mood swings.

Others see social lability in a positive light: such people easily make new acquaintances. While this may not be an advantage in personal life, it’s invaluable for networking.

Causes of Lability

Since lability is a borderline phenomenon involving both the mind and body, its causes are found in both areas.

Physiological (Autonomic) Causes

• Buerger’s disease
• Hormonal dysfunction
• Deficiency of nutrients essential for normal nervous system function
• Intoxication (from medications, drugs, alcohol, chemicals)
• Unstable blood pressure, frequent spikes
• Complications during or after pregnancy and childbirth
• Past stroke or heart attack
• Effects of unsuccessful anesthesia
• Brain tumors, traumatic brain injuries
• Thyrotoxicosis, hypothyroidism
• Severe neuroinfections: meningitis, encephalitis, myelitis, poliomyelitis, tetanus, HIV, cerebral malaria, etc.
• Epilepsy

Autonomic lability often develops alongside diseases such as Crohn’s disease, diabetes, kyphoscoliosis, lupus, Hodgkin’s lymphoma, late-stage cancer, and ulcers.

Psychological Causes

• Distress
• Spoiling (overindulgence)
• Lack of upbringing (not being taught self-control from childhood, leading to weakened inhibitory synapses that can’t stop emotional outbursts even if the person wants to)
• Psychological trauma
• Attention deficit hyperactivity disorder (ADHD)
• Excessive emotional stress

Intellectual lability is believed to be largely hereditary. Some experts think it can’t be corrected because it’s genetically determined. However, training and constant development of memory and attention can improve it, challenging this view.

Symptoms of Lability

If a person’s nervous system is labile, it will show on different levels. The clinical picture is usually obvious. In response to external stress, the autonomic nervous system activates the body’s defense mechanisms. Since inhibitory impulses can’t stop the excitatory wave in time, physiological symptoms appear instantly.

At the same time, the psyche experiences a similar process. The central nervous system sends the brain a task to handle the situation, and the brain responds with a powerful reaction that inhibitory synapses can’t stop—resulting in an emotional outburst.

Sometimes these symptoms occur together; sometimes, autonomic symptoms dominate over psychological ones (or vice versa). The clinical picture may include:

Psycho-Emotional Signs

• Short temper, impulsiveness
• Loud, uncontrollable, hysterical laughter
• Hysterical fits
• Reckless actions
• Irritability, anger, aggression
• Sudden mood swings
• Speech dysfunction (e.g., stuttering)
• Tears, crying, capriciousness
• Spontaneous, unexpected reactions
• Excessive emotionality

Frequent breakdowns can lead to insomnia, neurotic phobias, and panic attacks. In a crisis, things can get even worse: unable to control their emotions, a person may become dangerous to themselves and others (including risk of suicide).

It’s important to differentiate these states from mental disorders. The main difference is mood lability: outside of such situations, the person is completely adequate. There is almost always an overlap with physiological symptoms.

Physiological Signs

• Blood pressure spikes or drops suddenly
• Dizziness, “the ground falls away,” or seeing spots before the eyes
• Tremors or numbness in the limbs
• Rapid heartbeat (tachycardia), ringing in the ears, feeling like the heart will jump out of the chest
• Shortness of breath
• Increased sweating (forehead, underarms, palms become wet)
• Heightened sensitivity: sounds seem louder, lights seem brighter, even slight touches can hurt
• Severe migraines
• Auditory hallucinations

Outside of stressful situations, the person is completely healthy. Once the autonomic nervous system realizes there’s no danger, excitatory synapses quiet down, and within five minutes, the person returns to normal as if nothing happened. However, frequent episodes can lead to decreased libido, irritable bowel syndrome, weakened immunity, cystalgia, and other serious health issues.