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Blood platelets, due to shared biochemical and functional properties with presynaptic serotonergic neurons, constituted, over the years, an attractive peripheral biomarker of neuronal activity. Therefore, the literature strongly focused on the investigation of eventual structural and functional platelet abnormalities in neuropsychiatric disorders, particularly in depressive disorder. Given their impact in biological psychiatry, the goal of the present paper was to review and critically analyze studies exploring platelet activity, functionality, and morpho-structure in subjects with depressive disorder.
According to the PRISMA guidelines, we performed a systematic review through the PubMed database up to March 2020 with the search terms: (1) platelets in depression [Title/Abstract]”; (2) “(platelets[Title]) AND depressive disorder[Title/Abstract]”; (3) “(Platelet[Title]) AND major depressive disorder[Title]”; (4) (platelets[Title]) AND depressed[Title]”; (5) (platelets[Title]) AND depressive episode[Title]”; (6) (platelets[Title]) AND major depression[Title]”; (7) platelet activation in depression[All fields]”; and (8) platelet reactivity in depression[All fields].”
After a detailed screening analysis and the application of specific selection criteria, we included in our review a total of 106 for qualitative synthesis. The studies were classified into various subparagraphs according to platelet characteristics analyzed: serotonergic system (5-HT2A receptors, SERT activity, and 5-HT content), adrenergic system, MAO activity, biomarkers of activation, responsivity, morphological changes, and other molecular pathways.
Despite the large amount of the literature examined, nonunivocal and, occasionally, conflicting results emerged. However, the findings on structural and metabolic alterations, modifications in the expression of specific proteins, changes in the aggregability, or in the responsivity to different pro-activating stimuli, may be suggestive of potential platelet dysfunctions in depressed subjects, which would result in a kind of hyperreactive state. This condition could potentially lead to an increased cardiovascular risk. In line with this hypothesis, we speculated that antidepressant treatments would seem to reduce this hyperreactivity while representing a potential tool for reducing cardiovascular risk in depressed patients and, maybe, in other neuropsychiatric conditions. However, the problem of the specificity of platelet biomarkers is still at issue and would deserve to be deepened in future studies.
Chapter 1 looks at the notion of political leadership and presents an overview of the few works that have addressed the topic in the political science literature. The study of African politics departs from mainstream political science in that it has traditionally underscored the role that individual power-holders play in sub-Saharan polities. Single-party and military authoritarian rule has been the perfect ground for neopatrimonial regimes to flourish in Africa, and the latter, in turn, have favoured the weakening of African states and the gradual deterioration of political stability, economic development, and social welfare. While political leadership has often been considered a key cause of political and economic decay in postcolonial Africa, however, the leadership/development linkage has never been examined in a systematic manner. The new electoral regimes introduced in the region since the 1990s have been intended to redress the unsuccessful development trajectories of African states by altering the way in which national leaders reach and leave power and thus their political incentives for more effective policies
Chapter 3 presents the Africa Leadership Change (ALC) dataset, an original and comprehensive dataset designed to give better and fuller account of the various modes in which sub-Saharan leaders attain and abandon power, as well as to examine the evolution of these processes. The Africa Leadership Change dataset covers all changes in a country’s top political office (be this a presidential, a prime ministerial, or a king’s position) in all sub-Saharan states from 1960, or subsequent year of independence, to 2018. The dataset covers the complete historical series of leaders who were in power south of the Sahara in that period. It details how they entered power and how they left it; the amount of time that they spent in office; the changing sources of their power and legitimacy during their tenure; the country’s main political arrangements under their rule; a country’s frequency of leadership changes, and several other related aspects
Chapter 4 provides a detailed picture of key empirical trends in Africa’s leadership changes. It compares, in particular, the pre-1990 period with the post-1990 one. It shows that the primary effect of the new multiparty political arrangements has been a drastic reduction in the incidence of coups d’état and containment of African strongmen’s average duration in power. In many cases, elections helped impose an endpoint on the incumbent’s terms of office – often with the help of constitutional limits – forcing ruling parties to organize an internal succession process with a view to retaining the country’s presidency. In a more limited but highly significant number of cases, the outcome of the election has led to alternation in power between opposite political forces. What was only an exceptional occurrence between 1960 and 1989 has become considerably more common over the past 30 years.
Chapter 6 explores the highly mediatized issue of constitutional limits to the number of mandates that African presidents can serve, whether consecutively or not. It looks at how term limits were widely adopted on the continent during the reforms of the 1990s, and how in many countries they became the object of fierce political struggles and social tensions that in a number of cases turned violent. We look at the factors that explain why some leaders respected the term limits to which they were subject, while others tried to bypass such constraints, and, among the latter group, why some succeeded while others failed. The role of constitutionally limited mandates is examined in the broader context of the changing dynamics of leadership duration in office and increased rotation in power. Finally, the comparatively few cases of dynastic or familial successions in office are discussed to complete this overview of unlimited (and post-death) continuity in power
Chapter 9 resumes a widely known conceptualiztion of leadership in postcolonial Africa – the one formulated by Jackson and Rosberg in the early 1980s – and updates it to illustrate the most recurrent features and practices displayed by sub-Saharan power-holders by including the predominant leadership styles and behaviors that have emerged following the political reforms of the late twentieth century. A revised typology identifies four main leadership types on the continent, namely "transients," "autocrats," "hegemons," and "democrats." Only the latter two types – hegemons and democrats – are leaders operating within multiparty frameworks, although hegemons do not normally allow important political and electoral challengers to emerge, whereas democrats by and large do so. Finally, we also carry out a brief analysis of an understudied topic, that of the peculiar role of interim leaders (i.e., leaders who remain in office for less than one year), with a focus on the frequency with which they made their appearance – over time and across different countries – and on whether short-term rule was related to specific political developments
Political leaders loom large in African politics and development processes. They took center stage in public life after newly independent states emerged in the region, mostly in the early 1960s, and they grew ever more prominent over the better part of subsequent decades, favored by a widespread and persistent weakness of political institutions. As the developmental failures of most sub-Saharan economies became manifest, particularly from the 1980s onward, the ruinous leadership of many among them became obvious, if often only implicitly.
Chapter 2 presents the general framework we adopt to examine the impact of leadership changes. In Africa, unregulated stays in office by political leaders have coincided with the high personalization of authoritarian power, with the spread of neopatrimonial practices and with a growing disregard for public goods and government performance. We expect that the performance of African leaders should have improved after the adoption of political reforms in the 1990s. Democracy affects how leaders reach and leave power and what they do while they are in office. Electoral concerns induce them to be more mindful of the consequences of their government actions. Moving a step further, however, we hypothesize that also multiparty elections short of democracy may generate an impact on performance – particularly in an African context where mechanisms for selecting leaders and holding them accountable were previously in such short supply. We thus work within the stream in democratization studies that focuses on the socioeconomic consequences of political regimes. The specific perspective that we adopt, however, is one in which leadership change and alternation in power through multiparty elections constitute a key link between politico-institutional arrangements and mechanisms, even when they do not fulfill democratic standards, and performance outcomes
Chapters 7 considers the impact of leaders’ duration in power and of the diverse modes of leadership transfers on economic growth. It is postulated that electoral competition and alternation in office – even when they fall short of genuine democracy – help African citizens improve the accountability of their leaders, at least to some extent. The risk of being removed from power generates incentives to provide public goods for incumbents who want to maximize their reelection chances. At the same time, elections help opposition parties monitor the behavior of rulers and expose wrongdoings and maladministration. We advance several specific hypotheses on the effect that leaders can have on economic progress. We test these hypotheses empirically using a time-series and cross-sectional research design that includes all the 49 countries of the sub-Saharan region between 1960 and 2018. Much of the evidence confirms our underlying argument about African development, political leaders, and the modes in which they rotate in office matter
Chapter 5 focuses on military coups. It begins by examining the root causes and the practice of such irregular takeovers, which featured so prominently in postcolonial politics. Data show significant cross-regional differences. West Africa displays a particularly high frequency of coups (a feature shared with Central Africa), an above-average number of leaders per country, and a correspondingly lower length of stay in office. Southern Africa, by contrast, has the highest incidence of multiparty elections and the lowest occurrence of military interventions and other violent takeovers. For some time, the continent appeared to stand out, among comparable world regions, in terms of the permanence of coups as relatively recurrent political events. Yet coups evolved from being a most common way of capturing office to a much less frequent phenomenon also in sub-Saharan Africa. Over the past two decades they were increasingly accompanied by immediate pledges, on the part of the soldiers seizing power, that political authority would be rapidly handed back to civilian rulers via the introduction, or reintroduction, of competitive elections. Some observers went as far as to suggest that coups may be "good" for democracy. But the democratic as well as the developmental performance of most golpistas remains disappointing
Chapters 8 complements Chapter 7 by assessing the developmental implications of leadership changes in Africa through an extensive empirical analysis. It examines the impact of leaders’ duration in power and of the diverse modes of leadership transfers on the provision of social welfare, state consolidation and control of corruption. It is postulated that electoral competition and alternation in office – even when they fall short of genuine democracy – help African citizens improve the accountability of their leaders, at least to some extent. The risk of being removed from power generates incentives to provide public goods for incumbents who want to maximize their reelection chances. At the same time, elections help opposition parties monitor the behavior of rulers and expose wrongdoings and maladministration. We advance several specific hypotheses on the effect that leaders can have on social progress as well as on a better and less corrupt functioning of state apparatuses. We test these hypotheses empirically using a time-series and cross-sectional research design that includes all the 49 countries of the sub-Saharan region between 1960 and 2018. Much of the evidence confirms our underlying argument about African development, political leaders, and the modes in which they rotate in office matter
Chapter 10 draws the conclusions of our empirical analyses by summing up the broader implications of the changes in the ways that leaders reach and leave power south of the Sahara for the development processes in the region and their future prospects. As vast and consequential the transformations undergone by Africa’s political landscape and related leadership dynamics have been, so too are the challenges that lie ahead for the continent at a time when democratic ideals and practices have come increasingly under attack across the globe