Background and objectives. Internet addiction (IA) is characterized by excessive or poorly controlled preoccupations, urges or behaviours regarding computer use and internet access that lead to functional impairment or distress. Aim of the current research has been the analysis of the effect size of the multiple variables responsible for internet addiction in medical students. Methods. The current study is a cross-sectional and descriptive co-relational design. The opportunistic sample included 666 undergraduate medical students enrolled in the Medicine Bachelor and Bachelor of Science (MBBS) in a major medical university in India. Data analysis included meta-analysis for the coefficient of heterogeneity I2, Z-statistics and the effect size Cohen’s d. Results. High effect size (d>1.0) were shown by the prevalence of IA (d=5.40), gender (d=4.85), area of residence (d=2.60), level of depression (d=1.79), level of anxiety (d=2.99) and level of stress (d=1.98). The correlation of IA scale with psychiatric scale also showed a high effect size (d=2.40). IA presents with higher effects size in female students with moderate levels of anxiety. Discussion. Overall, our results support previous findings of a strong relationship between Internet addiction and psychological states such as depression, anxiety and stress.