What causes sudden conversion disorder?

What Causes Sudden Conversion Disorder?

Conversion disorder (functional neurological disorder) develops through multiple pathways, most commonly triggered by physical illness or injury (37% of cases), rather than psychological trauma alone, and does not require identifiable psychological stressors for diagnosis. 1

Primary Triggering Mechanisms

The causes of sudden conversion disorder are multifactorial and often misunderstood:

Physical Precipitants (Most Common)

• Physical illness or injury triggers symptoms in 37% of patients, including upper respiratory tract infections, voice overuse, injury to the face/mouth/oropharynx/larynx, and traumatic head injury 2, 1
• Physical stressors are as common as psychological ones in precipitating conversion symptoms 1
• The traditional assumption that psychological trauma must precede conversion symptoms is not supported by current evidence 2, 1

Psychological and Social Stressors

• Recent life events, particularly work-related and relationship difficulties, correlate with symptom severity when they occur in the year before onset 3
• In-law problems are associated with cognitive symptoms (p=0.036), while relationship difficulties more commonly precede expressive speech problems (p=0.021) 4
• However, stressful life events occur in equal proportions (20%) in patients with and without conversion disorder, indicating they are not specific triggers 1
• Most patients (92%) report some stressors associated with symptom onset, but these are not always identifiable or causative 4

Childhood Trauma (Variable Role)

• Childhood traumatization shows highly variable prevalence, ranging from 0% to 85% across studies, indicating it is neither necessary nor sufficient for diagnosis 1
• When present, early trauma combined with recent life events creates a cumulative stress effect that influences symptom severity 3

Important Diagnostic Clarifications

What Does NOT Cause Conversion Disorder

• The absence of psychological stressors does not exclude the diagnosis 2, 5
• Major adverse life events or clinically diagnosable psychological distress are not required 2
• The classic "la belle indifference" occurs in only 3% of conversion disorder patients versus 2% of controls, making it diagnostically useless 1

Modern Understanding

• DSM-5 removed the requirement for temporal relationship between psychological factors and symptom onset, recognizing that this criterion lacked empirical support 1
• The diagnosis now emphasizes positive neurological signs that are "incompatible with or not better explained by other recognized neurological or medical conditions" 2
• Conversion disorder represents a disorder of function with aetiological neutrality, not necessarily a purely psychological condition 2

Clinical Pitfalls to Avoid

• Do not assume psychological trauma must be present - this outdated requirement has been abandoned in DSM-5 1
• Do not dismiss physical precipitants - they are actually more common than purely psychological triggers 1
• Do not require identification of specific stressors before making the diagnosis - they cannot be found in a substantial proportion of cases 5
• Do not confuse absence of obvious stressors with malingering - feigning is very difficult to prove or disprove and should not be a primary diagnostic consideration 5

Multifactorial Stress Model

Current evidence supports replacing unifactorial trauma theories with a multifactorial stress model that includes: 3

• Physical illness or injury as primary trigger 2, 1
• Recent life events (particularly work and relationship stressors) 3
• Possible contribution from early childhood experiences 3
• Individual neurobiological vulnerability (mechanism still under investigation) 5

The key clinical takeaway is that conversion disorder can develop suddenly following physical illness or injury without any identifiable psychological precipitant, and clinicians should not delay diagnosis or treatment while searching for psychological explanations that may not exist 2, 5, 1.