The aim of this study was twofold. Firstly, it explored the relationships between morningness, Big Five personality traits, depression, and problematic Internet use (PIU). Secondly, it examined the possible mediating role of depression in these relationships. The following measures were used: the Internet Addiction Test, the Composite Scale of Morningness, the International Personality Item Pool-Big Five Markers-20, and the Center for Epidemiologic Studies Depression Scale. The participants in the study were 398 university students 18 to 30 (M = 20.37, SD = 2.29) years of age. The study found that PIU Total, PIU Mental Disorder, and PIU Time Management Disorder are positively related to depression and negatively related to morningness, Extraversion, Agreeableness, Conscientiousness, Emotional Stability, and Openness. PIU was more often found in individuals with an evening chronotype. The study confirmed the role of depression as a mediator in the relationship of personality traits and morningness to PIU Mental Disorder and PIU Time Management Disorder. For PIU Mental Disorder, the study revealed a full mediation effect of depression in the case of morningness, Emotional Stability, and Extraversion, and partial mediation in the case of Agreeableness and Intellect. For PIU Time Management Disorder, there was a full mediation effect of depression in the case of Emotional Stability, Extraversion, and Agreeableness, and partial mediation in the case of morningness and Intellect. The results highlight the importance of including depression when investigating the relationship between morningness and personality in studies of PIU.
Keywords: Big Five personality traits; Chronotype; Internet addiction; depression; problematic Internet use; young adults.