A range of potential mechanisms and aetiological factors in patients with functional motor disorders
| Factors | Biological | Psychological | Social |
|---|---|---|---|
| Factors acting at all stages | ▸ ‘Organic’ disease ▸ History of previous functional symptoms | ▸ Emotional disorder ▸ Personality disorder | ▸ Socio-economic/deprivation ▸ Life events and difficulties |
| Predisposing vulnerabilities | ▸ Genetic factors affecting personality ▸ Biological vulnerabilities in the nervous system | ▸ Perception of childhood experience as adverse ▸ Personality traits ▸ Poor attachment/coping style | ▸ Childhood neglect/abuse ▸ Poor family functioning ▸ Symptom modelling of others |
| Precipitating mechanisms | ▸ Abnormal physiological event or state (eg, drug side effect hyperventilation, sleep deprivation, sleep paralysis) ▸ Physical injury/pain | ▸ Perception of life event as negative, unexpected ▸ Acute dissociative episode/panic attack. | |
| Perpetuating factors | ▸ Plasticity in CNS motor and sensory (including pain) pathways leading to habitual abnormal movement ▸ Deconditioning ▸ Neuroendocrine and immunological abnormalities similar to those seen in depression and anxiety | ▸ Illness beliefs (patient and family) ▸ Perception of symptoms as being irreversible ▸ Not feeling believed ▸ Perception that movement causes damage ▸ Avoidance of symptom provocation ▸ Fear of falling | ▸ Social benefits of being ill ▸ Availability of legal compensation ▸ Ongoing medical investigations and uncertainty ▸ Excessive reliance on sources of information or group affiliations which reinforce beliefs that symptoms are irreversible and purely physical in nature |
Adapted from Stone and Carson.13
CNS, central nervous system.