In order to stop the spread of the COVID-19 to the campus, the Ministry of Education requested to postpone the start of school in the spring of 2020. In the spring of 2022, some colleges and universities were also procrastinated due to the pandemic. For young adults, extended vacations, long-term home stay, less going out, and unable to go to school to study and socialize normally may affect their studies and aggravate psychological stress reactions such as anxiety and depression [
31‐
33]. The theory of interaction between individuals and environment points out that individual behavior problems are the result of interaction between individual factors and environmental factors [
34]. Studies have shown that there is a significant negative correlation between family cohesion and Smartphone addiction. Liu Shihong defined family cohesion as the degree of emotional connection with family members that individuals feel. The better the family atmosphere [
35], the more communication, the less abnormal behavior individuals will have [
36]. In terms of environmental factors, the family is one of the micro systems that directly affect the psychological development of young people. Compared with other family variables (such as family upbringing, parent–child communication), family cohesion can better measure the overall atmosphere of the family and is a comprehensive indicator that reflects the positive family atmosphere and the close relationship between family members [
37]. Family environment factors, including the attitude of raising children, family communication and cohesion, can protect the excessive use of the Internet and addictive behavior [
38]. Other researchers found that family environmental factors, such as family structure, parents’ behavior, and family socio-economic status, can affect individual sleep quality and sleep time in various ways [
39]. Missildine proposed that the “procrastination syndrome” was caused by parenting styles, including over forcing children and setting unrealistic goals [
40]. When children cannot meet their parents’ expectations, they will begin to feel anxious and unworthy of doing, which will lead to procrastination [
41]. Aggressive parenting styles such as corporal punishment in parenting styles have a significant negative correlation with family cohesion [
42]. During the pandemic period, young adults procrastinated their school start and stayed at home longer. Based on this, this study proposes the hypothesis3: family cohesion moderates the relationship between psychological stress behavior and Smartphone addiction, psychological stress behavior and bedtime procrastination, as well as Smartphone addiction and bedtime procrastination (Fig.
1).