Smart homes are becoming increasingly common, bringing convenience to users but also raising serious security concerns. As the number of connected devices grows, so does the research interest in securing smart homes. However, the literature is broad, making it difficult to understand the main research directions and how they are connected. Given the scope and diversity of existing research, a systematic mapping study was chosen to provide a high-level overview of smart home security research by mapping research communities, identifying dominant themes, and examining their evolution over time. We retrieved articles from the Scopus database published between 2000 and April 2025, resulting in approximately 13,600 articles. After filtering out unrelated domains such as smart vehicles, smart industry, and general IoT, a final set of 6313 publications specifically focused on smart home security was used for analysis. We applied a citation-based network analysis approach, constructed an author citation graph, and used the Louvain community detection algorithm to identify 12 main research communities. Each community was further analyzed based on its keywords, most-cited publications, leading authors, and institutions. Our results provide a structured overview of the field, highlighting its key themes and evolution over time. This work can help researchers better navigate the smart home security landscape and identify future research opportunities.