Studies have reported elevated rates of dissociative symptoms and comorbid dissociative disorders in functional neurological disorder (FND); however, a comprehensive review is lacking.

To systematically review the severity of dissociative symptoms and prevalence of comorbid dissociative disorders in FND and summarise their biological and clinical associations.

We searched Embase, PsycInfo and MEDLINE up to June 2021, combining terms for FND and dissociation. Studies were eligible if reporting dissociative symptom scores or rates of comorbid dissociative disorder in FND samples. Risk of bias was appraised using modified Newcastle–Ottawa criteria. The findings were synthesised qualitatively and dissociative symptom scores were included in a meta-analysis (PROSPERO CRD42020173263).

Seventy-five studies were eligible (FND n = 3940; control n = 3073), most commonly prospective case–control studies (k = 54). Dissociative disorders were frequently comorbid in FND. Psychoform dissociation was elevated in FND compared with healthy (g = 0.90, 95% CI 0.66–1.14, I2 = 70%) and neurological controls (g = 0.56, 95% CI 0.19–0.92, I2 = 67%). Greater psychoform dissociation was observed in FND samples with seizure symptoms versus healthy controls (g = 0.94, 95% CI 0.65–1.22, I2 = 42%) and FND samples with motor symptoms (g = 0.40, 95% CI −0.18 to 1.00, I2 = 54%). Somatoform dissociation was elevated in FND versus healthy controls (g = 1.80, 95% CI 1.25–2.34, I2 = 75%). Dissociation in FND was associated with more severe functional symptoms, worse quality of life and brain alterations.

Our findings highlight the potential clinical utility of assessing patients with FND for dissociative symptomatology. However, fewer studies investigated FND samples with motor symptoms and heterogeneity between studies and risk of bias were high. Rigorous investigation of the prevalence, features and mechanistic relevance of dissociation in FND is needed.

Literature on childhood Functional Neurological Disorders (FNDs) is spare. Clinical presentations are vaguely characterized and often misdiagnosed in younger ages. Their main neurological features enrol: Psychogenic non-epileptic seizures (PNES), Functional movement disorders (FMDs), sensory alterations, cephalgia and feeding problems.

The study was aimed to better characterize the childhood population of FND, because of they represent an emerging challenge for clinicians, giving its higher presentation in the younger age and the difficulties of an early and differential diagnosis as well as an effective management.

Our study retrospectively examined the characteristics of 82 FNDs children and adolescents (8 to 16 y.o.; 13 males; 29 females) referred as neurological inpatients of an urban academic neuropsychiatric department, from 2014 to 2019. Three main clinical aspects were analysed: type and pattern of symptoms manifestations (DSM-5 criteria); Life Events; family functioning.

FND accounted for 2% of 5-years consultations of neurological inpatients (M: F=1:2). The clinical presentation was characterized in 70% by pattern of co-expressed neurological symptoms: FMDs (9.5%); PNES (12%); dizziness/lipothymia (12%); paraesthesia/anaesthesia (16%). Generalized pain was associated in 38% of the reported patterns while cephalgia in 44%. Sleep disorders were reported in 40%. Previous psychiatric diagnoses were uncommon (2 out 82). Antecedent stressors were identified in 97% of patients for personal illness history and in the 93% for chronic illness in the family anamnesis. Family problems were in 25% of cases.

Our data contributes to better characterize the childhood population of FND, describing clinical patterns of presentation, highlighting putative antecedent stressors and risk factors

Amongst different subtypes of Conversion Disorder (CD), DSM-V lists the Psychogenic Non-epileptic seizures (PNES). PNES are defined as episodes that visually resemble epileptic seizures but, etiologically, they are not due to electrical discharges in the brain.

Our study aims to explore the differences between PNES and other CDs. In particular, we studied the suicidality and its correlations with dissociation and alexithymia.

Patients, recruited from the Psychiatry and Clinical Psychology Unit of the Fondazione Policlinico Tor Vergata, Rome, Italy, were diagnosed with PNES (n=22) and CD (n=16) using the DSM-5 criteria. Patients underwent the following clinical assessments: HAM-D, BDI, DES, BHS, TAS, CTQ.

PNES showed significantly higher scores than CD in all assessments, except for BDI-somatic (p=0.39), BHS-feeling (p=0.86), and the presence of childhood trauma. PNES also showed significantly higher suicidality (p = 0.003). By controlling for the confounding factor “depression”, in PNES suicidality (and in particular the BHS-loss of motivation) appears to be correlated with DES-total score (p = 0.008), DES-amnesia (p = 0.002) and DES -derealization-depersonalization (p = 0.003). On the other hand, in CDs, the BHS-total score shows a correlation with the TAS-total score (p = 0.03) and BHS-Feelings with TAS-Externally-Oriented Thinking (p = 0.035), while only the BHS-Loss of motivation appears correlated with DES-Absorption (p = 0.011).

Our study shows significant differences between PNES and CD, in several symptomatologic dimensions, including suicidality. Indeed, in PNES suicidality appears to be related to dissociation, while in CDs it appears mainly to be correlated with alexithymia.

Dissociative seizures (DS) are brief episodes of disrupted awareness and behavioural control that may resemble epileptic seizures. They are thought to arise in the context of impaired emotion processing and disinhibition. In a multi-perspective neuropsychological study, we aim to assess specific metacognitive traits and behavioural features involved in the affective and cognitive underpinnings of DS (emotion recognition and regulation, inhibition, interoception and sense of agency).

Twenty prospectively recruited patients with video-EEG-confirmed DS and 20 healthy controls underwent comprehensive neuropsychological and psychiatric testing using validated questionnaires and structured interviews. Behavioural experimental data was obtained using a custom-made emotional go/no-go task, a digital Libet clock setup and a heartbeat counting paradigm.

Emotion recognition, as quantified in the emotional go/no-go task, was impaired in the DS group, and correlated with alexithymic traits. Behavioural inhibition, especially under conditions that would require emotion regulation, was also reduced in the emotional go/no-go task compared to controls and was correlated with neuropsychometric measures of emotion regulation. Data from the Libet clock experiment suggested impaired behavioural awareness in DS patients. No evidence of impaired interoceptive awareness was found in the heartbeat counting task.

These results represent comprehensive experimental evidence for alterations in emotional and behavioural awareness and control in patients with DS that yield empirical evidence for current psychopathological models. Our findings offer a more detailed understanding of key pathogenic factors in DS and provide theoretical support for recently developed cognitive-behavioural therapies for DS.

Informed consent was obtained from the patient for publication of Box 1.

None.