Tolchin 2019.

Study characteristics
Methods	Study design: randomised controlled trial Study grouping: parallel group Adequate power (evidence of power calculation): no power calculation Allocation concealment method: sequentially numbered opaque envelopes were used to conceal allocation until after baseline assessments were completed. Blinding of outcome assessors: yes. Telephone interviewers blinded to study arm assessed participants for adherence to psychotherapy, weekly PNES frequency, 4‐week seizure freedom, and monthly emergency department visits, and administered the QOLIE10 instrument. Participants were instructed not to reveal their group assignment to the interviewer and to avoid use of treatment language or terminology. Events where the blind was broken were tracked. Check of blinding: yes Duration of study: 16 weeks Randomisation method: 1:1 ratio using the Stata function RUNIFORM
Participants	Baseline Characteristics Intervention n: 29 Duration of symptoms: not reported Age (mean): 39.6 (SD 16.8) years Sex (% woman): 79% Ethnicity: 69% white Marital status currently married: not reported Educational status (mean duration of education): 13.0 (SD 2.7) years Control n: 31 Duration of symptoms: not reported Age (mean): 40.7 (SD 14.3) years Sex (% woman): 84 Ethnicity: 65% white Marital status currently married: not reported Educational status (mean duration of education): 13.8 (SD 2.5) years Overall n: 60 Duration of symptoms: not reported Age: not reported Sex (% woman): not reported Ethnicity: not reported Marital status currently married: not reported Educational status: not reported Inclusion criteria: aged ≥ 18 years; diagnosed with documented PNES by board‐certified epileptologists at BWH via VEEG review of all types of habitual seizure‐like events, without epileptiform or electrocardiographic abnormalities immediately before, during or following the events and with semiologies (clinical signs and symptoms) that were consistent with PNES.  Exclusion criteria: active alcohol or drug‐use disorders; pregnancy; severe medical illness expected to prevent regular participation in psychotherapy; clinically judged significant cognitive impairment; lack of fluent spoken English (given concerns that MI may be less effective in the setting of significant cognitive impairment or when delivered via interpreter).
Interventions	Intervention characteristics Intervention Description: outpatient informational session in a multidisciplinary seizure clinic with an epileptologist, neuropsychiatrist, and social worker within 2–4 weeks following the diagnosis of PNES. Immediately followed by 30 minutes of MI in the seizure clinic, followed by 12 sessions of psychotherapy. Length of treatment: 16 weeks Longest follow‐up after end of treatment: none Comedications/other treatments while in the study: not reported Control Description: outpatient informational session in a multidisciplinary seizure clinic with an epileptologist, neuropsychiatrist, and social worker within 2–4 weeks following the diagnosis of PNES, followed 12 sessions of psychotherapy. Length of treatment: 16 weeks Longest follow‐up after end of treatment: none Comedications/other treatments while in the study: none
Outcomes	Dropout Outcome type: dichotomous Quality of life Outcome type: continuous Change in monthly emergency department visits Outcome type: continuous Decrease in seizure frequency Outcome type: continuous
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Randomization assignments to one of two study arms (psychotherapy alone vs psychotherapy preceded by a 30‐minute session of MI) were generated with a 1:1 ratio using the Stata function RUNIFORM. Randomization assignments were created before the study began."
Allocation concealment (selection bias)	Low risk	Quote: "sequentially numbered opaque envelopes were used to conceal allocation until after baseline assessments were completed."
Blinding of participants and personnel (performance bias) All outcomes	High risk	Quote: "Immediately following informational sessions, participants randomized to MI plus psychotherapy received 30 minutes of MI in the seizure clinic. MI was conducted by a board‐ certified neurologist (B.T.)." Quote: "Participants were instructed not to reveal their group assignment to the interviewer and to avoid use of treatment language or terminology." Comment: the study's principal investigator performed the intervention.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "At 16‐ week follow‐up, telephone interviewers blinded to study arm assessed participants for adherence to psychotherapy, weekly PNES frequency, 4‐week seizure freedom, and monthly ED visits, and administered the QOLIE‐10 instrument."
Incomplete outcome data (attrition bias) All outcomes	High risk	Comment: intervention had adherence of 65.4%, while control only had 31.0%. This did not seem comparable.
Selective reporting (reporting bias)	Low risk	Comment: matched study protocol.
Other bias	Unclear risk	Comment: the results were not presented for actual active participants (17 vs 9), but for the whole groups of both intervention and controls. This did not give a correct view of the effect.

AED: antiepileptic drug; APA: adjunctive physical activity; BAI: Beck Anxiety Inventory; BDI: Beck Depression Inventory; CBT: cognitive behavioural therapy; CGI: Clinical Global Impression; DSM‐III‐R: Diagnostic and Statistical Manual of Mental Disorders, Third Edition, Revised; DSM‐IV: Diagnostic and Statistical Manual of Mental Disorders 4th Edition; DSM‐IV‐TR: Diagnostic and Statistical Manual of Mental Disorders 4th Edition, Text Revision; EEG: electroencephalogram; EMU: emergency medical unit; FIM: Functional Independence Measure Motor; FMS: functional motor symptom; FNS: functional neurological symptom; GAF: Global Assessment of Functioning; GP: general practitioner; HADS: Hospital Anxiety and Depression Scale; HRSA: Hamilton Rating Scale for Anxiety; ICD‐10: International Classification of Diseases; ICIDH; International Classification of Impairments, Disabilities and Handicaps; IQ: intelligence quotient; IPI: interdisciplinary psychotherapeutic intervention; max: maximum; MI: motivational interviewing; n: number of participants; NEA: non‐epileptic attack; PI; paradoxical intention therapy; PMDRS: Psychogenic Movement Disorder Scale; PNES: psychogenic non‐epileptic seizures; QOLIE: Quality of Life in Epilepsy Inventory; RCC: routine clinical care; SC: standard care; SCL‐90; Symptom Checklist; SD: standard deviation; SDQ‐20: 20‐item Somatoform Dissociation Questionnaire; SF‐36: 36‐item Short Form; SHCS; Stanford Hypnotic Clinical Scale for Adults; SMC: standard medical care; SRSS; National Institute of Mental Health Self‐ Rating Symptom Scale; TAU: treatment as usual; VA: Veterans Affairs; VEEG: video‐electroencephalogram; VRMC; Video Rating Scale for Motor Conversion Symptoms; WHO: World Health Organization; WSAS: Work and Social Adjustment Scale.