The associations between pre-sleep smartphone use, negative life events and depressive symptoms among Chinese...

Depressive symptoms are common public health concern among undergraduate students. With the widespread use of smartphones, the association between smartphone usage duration and depressive symptoms has received extensive attention. Meanwhile, academic and life stress play key roles in the development of depressive symptoms.

To explore the independent and interactive effects of pre-sleep smartphone use duration and negative life events (NLEs; e.g., exam failure, romantic relationship breakdown) on depressive symptoms among undergraduate students.

From October to November 2022, a cluster sampling survey was conducted at a university in Shaanxi Province, China. A total of 21,227 undergraduates were included in the final analysis. Depressive symptoms were assessed using the Self-Rating Depression Scale (SDS). Consistent with the standard psychometric convention for this scale, the presence of depressive symptoms was determined using a binary cut-off, with a total SDS score ≥ 50 indicating clinically significant depressive symptoms. The results do not reflect a clinical diagnosis of depression. Binary logistic regression models were used to examine the effects of pre-sleep smartphone use duration and negative life events on depressive symptoms. Restricted cubic spline (RCS) regression was applied to assess dose-response relationships, and Relative Excess Risk due to Interaction (RERI) and Attributable Proportion due to Interaction (AP) were used to characterize their interaction effect.

The prevalence of depressive symptoms among participants was 15.6%, and 54.8% reported experiencing NLEs. Prolonged pre-sleep smartphone use and more NLEs were significantly associated with an increased risk of depressive symptoms in a dose-response manner. Compared with the 0-30 min/day group, the fully adjusted ORs were 1.436(95%CI: 1.254-1.644) for 31-60 min/day, 1.917༈95%CI༚1.697-2.166༉ for 61-120 min/day, and 3.005༈95%CI༚2.654-3.042༉for > 120 min/day. The highest risk was observed in the group with > 120 min/day use and more than one NLE (OR = 10.830, 95%CI: 8.786-13.365) versus the reference group (0-30 min/day use and no NLEs). RERI/AP values for one NLE combined with 31-60, 61-120, > 120 min/day use were 0.359/0.119, 0.770/0.203, 0.143/0.023; for more than one NLE, the corresponding values were 0.171/0.044, -0.106/-0.191, 1.085/0.100.

Both pre-sleep smartphone use and NLEs are significantly associated with depressive symptoms among undergraduate students in a dose-response manner, and exert a synergistic effect on depressive symptoms.