Effects of Smartphone Use on Sleep and Mental Health in Young Adults: Going Beyond Self-Report.

Background: Poor sleep has been associated with mental health concerns such as anxiety and depression. Prior evidence suggests that smartphone use may be a factor in poor sleep and mental ill-health in young adults, though most studies have relied on self-reported measures of smartphone use and sleep, which can be unreliable. This study used objective and subjective measures to examine the relationship between time spent using smartphones, sleep duration, quality, regularity, and symptoms of depression and anxiety in a sample of self-selected poor sleepers. Methods: Participants (N = 99; 70.7% female) wore an actigraph for 2 weeks to assess their habitual nightly sleep duration and regularity. Their average daily smartphone screen use was collected over 1 week with a smartphone application. Standardized questionnaires were used to assess sleep quality and mental health symptoms. Results: No statistically significant associations were found between objective smartphone screen use and any sleep or mental health variables. Sleep disturbance, sleep-related daytime impairment, anxiety, and depression were positively correlated. However, regression models identified that only sleep-related daytime impairment explained unique variance in anxiety and depression when adjusted for sleep disturbance and duration, gender, age, and screen time. Limitations: Specific timing of smartphone screen use (e.g., evening use) and/or application content were not collected as part of this study. Conclusions: These results conflict with prior evidence demonstrating negative relationships between self-reported smartphone screen use, sleep, and mental health. Further research incorporating objective measurement of smartphone screen use, focusing on critical periods for sleep, may provide a more nuanced picture of this relationship. Results also demonstrate the differing roles of night-time sleep disturbance and daytime sleep-related impairment in mental health. Trial Registration: Australian New Zealand Clinical Trials Registry number: ACTRN12621000132842.