Assistive social robots are believed to be useful in eldercare for two reasons, a functional one and an affective one. Such robots are developed to function as an interface for elderly to digital technology, and to help increase the quality of life of elderly by providing companionship respectively. There is a growing attention for these devices in the literature. However, no comprehensive review is yet performed to investigate the effectiveness of such robots in the care for elderly. Therefore, we systematically reviewed and analyzed existing literature on the effs of these devices.