Greenwich University

The serotonin hypothesis of depression is still influential. We aimed to synthesise and evaluate evidence on whether depression is associated with lowered serotonin concentration or activity in a systematic umbrella review of the principal relevant areas of research. PubMed, EMBASE and PsycINFO were searched using terms appropriate to each area of research, from their inception until December 2020. Systematic reviews, meta-analyses and large data-set analyses in the following areas were identified: serotonin and serotonin metabolite, 5-HIAA, concentrations in body fluids; serotonin 5-HT 1A receptor binding; serotonin transporter (SERT) levels measured by imaging or at post-mortem; tryptophan depletion studies; SERT gene associations and SERT gene-environment interactions. Studies of depression associated with physical conditions and specific subtypes of depression (e.g. bipolar depression) were excluded. Two independent reviewers extracted the data and assessed the quality of included studies using the AMSTAR-2, an adapted AMSTAR-2, or the STREGA for a large genetic study. The certainty of study results was assessed using a modified version of the GRADE. We did not synthesise results of individual meta-analyses because they included overlapping studies. The review was registered with PROSPERO (CRD42020207203). 17 studies were included: 12 systematic reviews and meta-analyses, 1 collaborative meta-analysis, 1 meta-analysis of large cohort studies, 1 systematic review and narrative synthesis, 1 genetic association study and 1 umbrella review. Quality of reviews was variable with some genetic studies of high quality. Two meta-analyses of overlapping studies examining the serotonin metabolite, 5-HIAA, showed no association with depression (largest n = 1002). One meta-analysis of cohort studies of plasma serotonin showed no relationship with depression, and evidence that lowered serotonin concentration was associated with antidepressant use ( n = 1869). Two meta-analyses of overlapping studies examining the 5-HT 1A receptor (largest n = 561), and three meta-analyses of overlapping studies examining SERT binding (largest n = 1845) showed weak and inconsistent evidence of reduced binding in some areas, which would be consistent with increased synaptic availability of serotonin in people with depression, if this was the original, causal abnormaly. However, effects of prior antidepressant use were not reliably excluded. One meta-analysis of tryptophan depletion studies found no effect in most healthy volunteers ( n = 566), but weak evidence of an effect in those with a family history of depression ( n = 75). Another systematic review ( n = 342) and a sample of ten subsequent studies ( n = 407) found no effect in volunteers. No systematic review of tryptophan depletion studies has been performed since 2007. The two largest and highest quality studies of the SERT gene, one genetic association study ( n = 115,257) and one collaborative meta-analysis ( n = 43,165), revealed no evidence of an association with depression, or of an interaction between genotype, stress and depression. The main areas of serotonin research provide no consistent evidence of there being an association between serotonin and depression, and no support for the hypothesis that depression is caused by lowered serotonin activity or concentrations. Some evidence was consistent with the possibility that long-term antidepressant use reduces serotonin concentration.

Later-life learning has been an object of theory and empirical research for decades. However, gaps remain in frameworks that can both recognize learners' agency and the impact of structural barriers. Envisioning a future of sustainable learning practices in later life, this position paper offers critical realism as a framework for researching later-life learning as situated within sustainable learning ecosystems. To that end, the authors first outline the main ontological and epistemological orientations of critical realism. Further, drawing on literature from educational sciences and aging studies, the authors explore the affordances of critical realism to theorize the causal mechanisms that inform learning in later life. What follows is a discussion of the practicalities and realities of the learning environments, and an argument that a critical realist framing clarifies what it takes to build adaptable learning ecosystems grounded in age equity and inclusion.

Global interest in plant-derived proteins continues to expand, largely due to increasing demand for sustainable and alternative nutritional sources. Within this framework, stinging nettle (Urtica dioica L.), a relatively underexploited leafy material with notable protein content, offers considerable potential as a novel protein source. This study evaluated the effects of three extraction approaches, alkaline extraction coupled with isoelectric precipitation (AE-IP), ultrasound-assisted extraction (UAE), and ultrafiltration (UF), on the structural, physicochemical, and techno-functional properties of nettle protein concentrates (NPCs). UAE resulted in the greatest protein recovery (41.62

Social media have become crucial for hotels to personalise communication in real time, yet the understanding of how real-time engagement influences both value co-creation and co-destruction remains limited. Adopting a time-as-process lens, this paper examines how the temporal dynamics of past experiences, present perceptions, and future anticipations interact within ongoing, situated real-time engagements, identifying critical moments of value co-creation and co-destruction. Drawing on a vignette-based role-playing design, the study simulates customer-manager interactions during a social media storm (SMS) to analyze how these temporal flows unfold in practice. The findings identify moments of engagement shaping value co-creation and co-destruction, providing hospitality managers with a more comprehensive understanding of how real-time social media engagement impacts service personalisation and its potential outcomes in terms of both positive and negative value exchanges.

This study investigates the experience of Black female leaders in UK business and the narratives of their lived experience of marginalization. Drawing principally on the rather small UK-focused literature on this topic as context, as well as some of the much larger international literature, methodologically we use the approach to qualitative inquiry developed by John Shotter. Shotter argued strongly for understanding human experience from the inside, in a social constructivist form of phenomenological investigation that views "data gathering" in such contexts as a dialog between the researcher and the subject. The main research question is: How do Black female leaders in the UK understand and experience the barriers and challenges of being marginalised in contemporary business? One of our main contributions of this research is the methodological shift: by advocating for Shotter's "withness/withinness" thinking, we encourage a shift away from objectifying marginalized subjects as research objects, towards co-created meaning-making. In addition, we contribute to academic discourse by proposing new insights that both reaffirm and challenge existing paradigms relating to, for example, the nuanced distinction between "glass" and "concrete ceilings" in conventional feminist leadership discourse. The data analysis identified three key themes relating to the intersectional identity of black female leaders, two of which represent the internal dimensions of the intersectional identity of these black leaders: (a) "The Perception of Difference" and (b) "the Perception of Self." The structural dimension of intersectional identity focuses on the "individual-organization relationship". Both internal and structural dimensions are part and parcel of intersectional identity of black female leaders.