BackgroundMobile phones are an important part of adolescents’ life. In this study, the relationships among smartphone addiction, age, gender, and chronotype of German adolescents were examined.Materials and methodsTwo studies focused on two different measures of smartphone addiction. The Smartphone Addiction Proneness Scale (SAPS) was applied to 342 younger adolescents (13.39 ± 1.77; 176 boys, 165 girls, and 1 not indicated) in Study 1 and the Smartphone Addiction Scale was applied to 208 older adolescents (17.07 ± 4.28; 146 girls and 62 boys) in Study 2, both samples in southwest Germany. In addition, a demographic questionnaire and the Composite Scale of Morningness (CSM) and sleep measures were implemented.ResultsThe most remarkable result of this study was that morningness–eveningness (as measured by CSM scores) is an important predictor for smartphone addiction; even stronger than sleep duration. Evening oriented adolescents scored higher on both smartphone addiction scales. In addition, gender is an important predictor for smartphone addiction and girls are more prone to become addicted. In addition, while sleep duration on weekdays negatively predicted SAPS, age, sleep duration on weekends, and midpoint of sleep on weekdays and weekends did not predicted smartphone addiction in both scales. The analysis of covariance revealed statistically significant effects of the covariates gender and age in both studies, as well as the main effect of chronotype. According to the t-test results, girls had higher scores than boys in smartphone addiction.ConclusionEvening types and girls are more prone to become smartphone addicted.

The present study investigates whether the circadian preferences of students are related to their academic achievements. This study explores whether different class times affect students' achievement and examines the performance of students on final exams administered at 09:30 h for differences according to chronotype. A total of 1471 university students between 18 and 25 yrs of age responded to a morningness-eveningness questionnaire (MEQ), and data on their cumulative grade point averages (CGPA) were also collected from their transcripts. Some of the students in the sample attended classes during the first teaching period, which started at 08:00 h and ended at 14:50 h, and the remaining students followed the second schedule, which started at 15:00 h and ended at 21:50 h. MEQ scores were found to differ by sex. MEQ scores partially predicted academic success and that students' academic achievements differed according to the time of the teaching period. Moreover, final exam (administered at 09:30 h) scores differed with respect to their circadian preferences; students with a morning preference achieved higher scores than either those with an evening or intermediate preference. Both teaching and test start times thus impact academic performance.

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The Composite Scale of Morningness is widely used and translated into several languages. The aim of the study was to present psychometric properties of Turkish version of CSM based on a sample of high school and university students. A total of 543 high school and 650 university students have participated in to the study. The internal consistency coefficient was found to be .73 (high school) and .80 (university). The test-retest reliability of the scale was .89 in high school sample and .84 in university sample. The mean CMS scores did not differ by gender in both samples. Exploratory and confirmatory factor analysis revealed that the scale is valid. As an external validation, morningness was associated with MEQ scores, sleep length, mid-point of sleep, rising and retiring time. The data obtained in the study suggested that the Turkish version of the CSM is a reliable and valid instrument to assess circadian preference in both high school and university samples.