A study involving 99 participants explored the link between smartphone use, sleep, and mental health, particularly anxiety and depression. The research utilized both objective and subjective measures to assess smartphone screen time and sleep patterns over a two-week period. Despite previous studies suggesting a negative impact of smartphone use on sleep and mental health, this study found no significant associations between actual smartphone usage and sleep quality or mental health symptoms. Instead, sleep disturbances and daytime impairments related to sleep were positively correlated with anxiety and depression. However, only daytime impairment uniquely contributed to anxiety and depression levels when accounting for other variables such as sleep disturbances, age, gender, and screen time. The study did not track the timing of smartphone use or the types of applications used, which could influence the findings. The researchers emphasize the need for further investigation using objective measurements of smartphone use during crucial sleep periods to better understand these relationships. The trial was registered with the Australian New Zealand Clinical Trials Registry.