In Portugal, research productivity is nowadays essential for the positive assessment of academics, research units and study programmes. Academic inbreeding has been highlighted in the literature as one of the factors influencing research productivity. This paper tests the hypothesis that inbreeding is detrimental for research productivity, measured through the number of publications listed in Scopus. The study resorts to a database provided by the national Agency for Assessment and Accreditation of Higher Education (A3ES), which comprises all academics teaching in all Portuguese institutions in the academic year 2015/2016. The sample selected for the analysis contains all academics with a PhD in Sociology (N=289). The study uses a special regression model for the analysis: the negative binomial logit hurdle. This was necessary given the large amount of academics with no publications or citations in Scopus, which were the dependent variables to assess research performance. The analysis provides separate results for the probability of inbred academics of having no papers/citations, and for the probability of producing more papers/citations than the non-inbred. Findings suggest that academic inbreeding, defined at the institutional level, has no negative effect on research productivity, contrary to what was expected. However, when defined at the national level, academic inbreeding is detrimental for the recognition and the impact of research: academics with a foreign PhD are more likely to have citations compared to academics who obtained their PhD in Portugal. A tendency was also noted that inbreeding might be more detrimental to research productivity in faculties of Economics than in Social Sciences and Humanities.