The influence of social network sentiment on stock market indices and companies has been proven in several studies. However, the influence of social network sentiment on sustainability indices and sustainable companies has not been analyzed so far. Therefore, this study analyzed the influence of social network sentiment on sustainability indices (S&P 500 Environmental & Socially Responsible Index) and focused on variations of this influence on sustainable and non-sustainable companies, namely, in companies included in the Information Technology sector. To this end, two methodologies were used: GARCH (1,1) models and logit-probit models. The results showed that social network sentiment influences S&P 500 Environmental & Socially Responsible Index’s volatility; this influence was greater than the influence of social network sentiment when considering the S&P 500 Index. Additionally, the results showed that social network sentiment influences sustainable companies’ returns but had no effect on unsustainable companies’ returns. These results highlighted the importance of managing the companies’ profiles in social networks and their corporate image in general, because investors will consider these aspects to design their investment strategies.

Organisational citizenship behaviour (OCB) can be defined as discretional, voluntary and useful informal behaviour that is not directly acknowledged by the organisation’s formal reward system. Such behaviour refers to actions that go beyond performing the tasks defined as part of one’s job. Previous studies have shown that organisations that promote OCB can notably improve their productivity and efficiency. It is therefore important to know what causes employees to engage in OCB rather than just limiting themselves to doing what is strictly expected at work. However, it is more important to know why they do not engage in OCB. Using a sample of public prison employees and the fsQCA method, this study examines how the combined effects of organisational characteristics, leadership behaviours and individual characteristics lead to the absence of OCB. The results indicate that the absence of affective commitment, or job satisfaction, or interactional justice is a necessary condition for the absence of OCB. Four conditions are identified as sufficient, and the absence of affective commitment and the presence of laissez-faire leadership are found to be the most relevant conditions for the absence of OCB. Managerial implications and directions for future studies are discussed at the end of the paper.