Three hypotheses have been suggested to explain factors underlying Internet gaming disorder symptoms (IGDs): the comorbidity hypothesis highlights the presence of further psychopathologies; the dilution effect hypothesis is associated with a low level of self-regulation; and the interpersonal impairment hypothesis focuses on the associations of social deficits. Anxiety and depression (comorbidity), impulsivity and hostility (self-regulation), social skills and family functioning (interpersonal impairment), and time spent gaming, both during the week and on the weekend, were assessed. Participants were 946 young people (51.5% males) aged from 11 to 18. Preliminary correlations indicated that higher scores in anxiety, impulsiveness, hostility, and social skills deficit and lower scores in family functioning and more time spent gaming were associated with IGDs. The proposed theoretical model had a good fit to the data, revealing that anxiety and time spent gaming on the weekend had a direct association with IGDs. Social skills and family functioning showed an indirect relationship with IGDs, whereas impulsivity only showed a direct association with time spent gaming during the week. However, a different set of variables was associated with IGDs depending on the gender. In girls, the significant variables associated with IGDs were time spent playing video games during the week and on the weekend, higher anxiety, and lower family functioning. In boys, direct associations between higher anxiety and hostility, social skill deficits, and time spent gaming on the weekend were found. Results support the three hypotheses, but their applicability varied according to gender. The comorbidity hypothesis was slightly superior for girls, whereas the dilution effect hypothesis was superior for boys. The factors involved in IGDs should be taken into account when designing interventions to prevent symptoms and their consequences.