A meta-analytic evaluation of the effectiveness and durability of psychotherapy for adults presenting with functional dissociative seizures

Background: Psychological interventions are the most recommended treatment for functional/dissociative seizures (FDS); however, there is ongoing uncertainty about their effectiveness on seizure outcomes. Methods: This systematic review and meta-analysis synthesises the available data. In February 2023, we completed a systematic search of four electronic databases. We described the range of seizure-related outcomes captured, used meta-analytic methods to analyse data collected during treatment and follow-up; and explored sources of heterogeneity between outcomes. Results: Overall, 44 relevant studies were identified involving 1,300 patients. Most were categorised as being at high (39.5 %) or medium (41.9 %) risk of bias. Seizure frequency was examined in all but one study; seizure intensity, severity or bothersomeness in ten; and seizure duration and cluster in one study each. Meta-analyses could be performed on seizure freedom and seizure reduction. A pooled estimate for seizure freedom at the end of treatment was 40 %, while for follow-up it was 36 %. Pooled rates for >= 50 % improvement in seizure frequency were 66 % and 75 %. None of the included moderator variables for seizure freedom were significant. At the group level, seizure frequency improved during the treatment phase with a moderate pooled effect size (d = 0.53). FDS frequency reduced by a median of 6.5 seizures per month. There was also evidence of improvement of the other (non-frequency) seizure-related measures with psychological therapy, but data were insufficient for metaanalysis. Conclusions: The findings of this study complement a previous meta-analysis describing psychological treatmentassociated improvements in non-seizure-related outcomes. Further research on the most appropriate FDSseverity measure is needed.