1.
Stress matters: Randomized controlled trial on the effect of probiotics on neurocognition.
Papalini, S, Michels, F, Kohn, N, Wegman, J, van Hemert, S, Roelofs, K, Arias-Vasquez, A, Aarts, E
Neurobiology of stress. 2019;10:100141
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Increasing animal studies indicate the role of probiotics in regulating mood and cognition through the gut-brain axis, however in human studies evidence of this causal association is lacking. The aim of this double-blind, randomised, placebo-controlled intervention was to investigate the effects of probiotics on neurocognitive measures in 58 healthy participants. Participants were randomly assigned to either probiotic or placebo group and were tested once before and after the 28-day intervention. The neurocognitive outcomes measured included emotion reactivity, emotion regulation, cognitive control and the effects of acute stress on working memory. These were assessed through functional MRI (fMRI) and questionnaires. This study found when stress was induced, probiotic supplementation led to a significant improvement in working memory performance. Without stress, there was no causal association between neurocognitive outcomes and probiotic intake. Based on these results, the authors conclude that during challenging situations, probiotics can aid in buffering the detrimental effects of stress on cognition.
Abstract
Probiotics are microorganisms that provide health benefits when consumed. In animals, probiotics reverse gut microbiome-related alterations in depression-like symptoms, in cognition, and in hormonal stress response. However, in humans, a causal understanding of the gut-brain link in emotion and cognition is lacking. Additionally, whether the effects of probiotics on neurocognition are visible only in presence of stress, remains unclear. We investigated the effects of a multispecies probiotic (Ecologic®Barrier) on specific neurocognitive measures of emotion reactivity, emotion regulation, and cognitive control using fMRI. Critically, we also tested whether probiotics can buffer against the detrimental effects of acute stress on working memory. In a double blind, randomized, placebo-controlled, between-subjects intervention study, 58 healthy participants were tested once before and once after a 28-day intervention. Without stress induction, probiotics did not affect brain, behavioral, or related self-report measures. However, relative to placebo, the probiotics group did show a significant stress-related increase in working memory performance after supplementation. This change was associated with intervention-related neural changes in frontal cortex during cognitive control exclusively in the probiotics group. Overall, our results show neurocognitive effects of a multispecies probiotic in healthy women only under challenging situations, buffering against the detrimental effects of stress on cognition.
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Stressful life events and maltreatment in conversion (functional neurological) disorder: systematic review and meta-analysis of case-control studies.
Ludwig, L, Pasman, JA, Nicholson, T, Aybek, S, David, AS, Tuck, S, Kanaan, RA, Roelofs, K, Carson, A, Stone, J
The lancet. Psychiatry. 2018;(4):307-320
Abstract
BACKGROUND Stressful life events and maltreatment have traditionally been considered crucial in the development of conversion (functional neurological) disorder, but the evidence underpinning this association is not clear. We aimed to assess the association between stressors and functional neurological disorder. METHODS We systematically reviewed controlled studies reporting stressors occurring in childhood or adulthood, such as stressful life events and maltreatment (including sexual, physical abuse, and emotional neglect) and functional neurological disorder. We did a meta-analysis, with assessments of methodology, sources of bias, and sensitivity analyses. FINDINGS 34 case-control studies, with 1405 patients, were eligible. Studies were of moderate-to-low quality. The frequency of childhood and adulthood stressors was increased in cases compared with controls. Odds ratios (OR) were higher for emotional neglect in childhood (49% for cases vs 20% for controls; OR 5·6, 95% CI 2·4-13·1) compared with sexual abuse (24% vs 10%; 3·3, 2·2-4·8) or physical abuse (30% vs 12%; 3·9, 2·2-7·2). An association with stressful life events preceding onset (OR 2·8, 95% CI 1·4-6·0) was stronger in studies with better methods (interviews; 4·3, 1·4-13·2). Heterogeneity was significant between studies (I2 21·1-90·7%). 13 studies that specifically ascertained that the participants had not had either severe life events or any subtype of maltreatment all found a proportion of patients with functional neurological disorder reporting no stressor. INTERPRETATION Stressful life events and maltreatment are substantially more common in people with functional neurological disorder than in healthy controls and patient controls. Emotional neglect had a higher risk than traditionally emphasised sexual and physical abuse, but many cases report no stressors. This outcome supports changes to diagnostic criteria in DSM-5; stressors, although relevant to the cause in many patients, are not a core diagnostic feature. This result has implications for ICD-11. FUNDING None.
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Stress, childhood trauma, and cognitive functions in functional neurologic disorders.
Roelofs, K, Pasman, J
Handbook of clinical neurology. 2016;:139-155
Abstract
Conversion disorder (CD) has traditionally been ascribed to psychologic factors such as trauma, stress, or emotional conflict. Although reference to the psychologic origin of CD has been removed from the criteria list in DSM-5, many theories still incorporate CD as originating from adverse events. This chapter provides a critical review of the literature on stressful life events in CD and discusses current cognitive and neurobiologic models linking psychologic stressors with conversion symptomatology. In addition, we propose a neurobiologic stress model integrating those cognitive models with neuroendocrine stress research and propose that stress and stress-induced changes in hypothalamus-pituitary-adrenal (HPA) axis function may result in cognitive alterations, that in turn contribute to experiencing conversion symptoms. Experimental studies indeed suggest that basal as well as stress-induced changes in HPA axis responding lead to alterations in attentional processing in CD. Although those changes are stronger in traumatized patients, similar patterns have been observed in patients who do not report a history of traumatic events. We conclude that, whereas adverse events may play an important role in many cases of CD, a substantial proportion of patients do not report a history of traumatization or recent stressful events. Studies integrating effects of stress on cognitive functioning in CD are scarce. We propose that, instead of focusing research on defining etiologic events in terms of symptom-eliciting events, future research should work towards an integrated mechanistic account, assessing alterations in cognitive and biologic stress systems in an integrated manner in patients with CD. Such an account may not only serve early symptom detection, it might also provide a starting point for better-targeted interventions.
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Changes in PTSD patients' narratives during prolonged exposure therapy: a replication and extension.
van Minnen, A, Wessel, I, Dijkstra, T, Roelofs, K
Journal of traumatic stress. 2002;(3):255-8
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Abstract
Following E. B. Foa, C. Molnar, and L. Cashman (1995), narrative changes from the first to the last exposure session were compared for improved and nonimproved PTSD patients on fragmentation, organization, internal, and external events. Improved (n = 8) and nonimproved (n = 12) patients did not differ regarding changes in fragmentation or organized thoughts. However, improved patients showed a greater decrease in disorganized thoughts during treatment. Furthermore, all patients, independent of improvement, showed significant changes in the same direction; a decrease in disorganized thoughts and external events and an increase in internal events. Although previous results were partly replicated, it is concluded that narrative changes may be due to exposure treatment itself rather than to changes in memory representation.