## 6 Conclusions  
Our research study revealed that SVREs are being used consistently across time in distance learning in HE for a wide array of subjects. SVREs effectively support learner-centered instructional e-learning approaches such as project- and collaborative problem-based learning. These methods appear to be effective towards DML in HE. Overall, 54% of the included studies (\(n=18\)) recorded positive learning effects in two of the three domains associated with DML; cognitive, social, or affective. Ten additional studies (30%) reported positive results in all three domains. The most common observed learning effects were performance gains, high levels of satisfaction, collaboration, and motivation. Analyzing these studies, we aggregated a model of fifteen critical factors for DML related to learners, design, and technology. The findings of this systematic literature review shed light on an era of slow adoption and use of distance learning through virtual learning environments. These research outcomes, in general, enhance understanding of the status of open and distance learning in higher education. The study and its outcomes also provide a particular focal point to the use of virtual learning environments in providing contributions to deep and meaningful learning (DML). From the theoretical and practical points of view, new guidelines and recommendations based on the literature review findings could support instructional design and improve teaching and learning practices across multiple subjects. Admittedly, early researchers of social virtual reality learning environments tend to have a positive and optimistic stance towards technology acceptance and benefits for the effectiveness of particular e-learning methods and tools. This tendency often overshadows ethical considerations and potential dangers in the short and long run. For example, problematic situations that easily arise from the use of SVREs such as online privacy and cyber security, cyber bullying, group-thinking, addiction, and many other psycho-somatic and cyber communication consequences are hardly mentioned, if at all. The reason for this neglect might not just be the well-known phenomenon of the subjectivity of the researcher--it could possibly be the general desire to reach successful e-learning outcomes in order to prove the use of e-learning environments as valuable for all stakeholders. E-learning stakeholders (e.g., learners, instructors, educational policy makers, academic leaders, and VR developers) can use the resulted socio-technical and pedagogic Blended Model for Deep and Meaningful E-learning in Social Virtual Reality Environments to identify and take into account all the interlinked factor categories that include individual, design-related, implementational, technological, and socio-technical aspects that mediate DML. From practical and historical points of view, the empirical data in this review provide valuable chronological information regarding DML in different eras of distance education. Thus, this review also contributes to the field by summarizing good teaching and learning practices worldwide and by providing analytical insights. In that sense, the review facilitates a culture shift towards active and personal learning in distance education by adopting learner-centered strategies. This can be a vehicle for a paradigm shift if it is combined with the required suitable guidance by a \"change agent of learning\" online or offline. The latter, that is an online/offline learning change agent, was lacking and sometimes proved to be one of the most critical aspects of the success of e-learning before and during the coronavirus crisis in distance mode learning. This particular learning item could be conceptualized and realized as an actual human component or learning interface item. In regard to social virtual learning environments, there seem to be a few under-researchedtopics increasing in popularity right now under the lens of pedagogic research projects internationally [6; 17; 48].