As the influence of social networking spreads across young people, it becomes exigent to explore how its problematic use relates to important psychological outcomes such as loneliness, happiness and interpersonal dependency. Three hundred fifty-six undergraduates, 184 =males and 172 = females from a university in southeast Nigeria participated in this study. Their ages ranged from 15 to 32 years (mean age of 20). Four questionnaires that measured each variable were used to collect data, and a correlation design was adopted for the study. Three hypotheses were tested and findings revealed that study variables significantly correlated with problematic use of social networking sites: Loneliness r = .18, p < .01, Happiness r= -.14, p < .01; Interpersonal Dependency r= .32, p <.01 and dimensions of Interpersonal dependency (Emotional reliance r = .31, p < .01; Lack of self-confidence r= .32, p < .01; and Assertion of autonomy r = .11, p < .05 . The discussion focused on the fact that social networking has the potentials of decreasing mental wellbeing and increasing the mental health challenges.