The COVID-19 pandemic has changed social and work life. It forced everyone to make changes to previous habits, and these changes had a big impact on sleep and mental well-being. In Poland, the lockdown began with the closure of schools and universities in the first half of March 2020. This was followed by restrictions on meetings outside the family circle to two people, and a ban on traveling for purposes other than higher necessity. Such a sudden change in social functioning was associated with stress and anxiety. The primary sources of stress were isolation, restrictions on movement and traveling, the requirement to wear face masks, frequent hand washing and disinfection, avoiding social contacts and meetings, closed restaurants, pubs, and fitness clubs, limiting physical activity even outdoors, as well as remote learning and online work [30]. Young people are more vulnerable to the effects of lockdown. It was particularly difficult for them due to the limitation of social contacts, which contributed to the deterioration of their mental health [31].
Studies by other authors indicate that sleep problems in adolescence may be caused by lifestyle, especially intensive learning and consumption of energy drinks and coffee [32- 34]. The cause of insomnia may be the rhythm of the day imposed by school duties. A 2010 New England study of 357 students showed that even a half-hour shift in the start time of school (from 8:00 a.m. to 8:30 a.m.) helped reduce the feeling of sleepiness and fatigue during the day and increased motivation to learn. Moreover, the authors proved that the number of students exhibiting depressive symptoms and experiencing anxiety and irritability decreased by one-fifth. The results of this study support the potential benefits of adjusting school schedules to adolescents' sleep needs, circadian rhythms, and developmental stage [35].
Our study found that nearly one-third of the subjects experienced increased sleep problems. A similar study was conducted by Marelli et al. (2021), who examined the association of the COVID-19 pandemic with sleep disturbances in a group of 400 Italians. They observed a significant increase in insomnia compared to the pre-pandemic state in both the student and university employee groups. What’s more, in this study, the authors showed that women felt the impact of the pandemic on sleep disorders more strongly than men, with over 30% of the subjects reporting depressive and anxiety symptoms for this reason [36].
Similarly, the presented studies showed a relationship between sex and insomnia—women reported insomnia and sleep disorders more often than men. Our results corresponded with those of Hasan et al. (2021) [37], who studied insomnia in young adults in Bangladesh and with a study by Taufig et al. (2021) who examined students during the Covid-19 pandemic [38].
Silva et al. (2020) showed that sleep disturbances during the pandemic, caused by mental strain and changes in the circadian rhythm, worsen the body’s immunity [39].
Based on the DSM-V criteria used in this study, insomnia was found in 29.5% of respondents aged 18-25, and the proportion of people reporting subjective sleep problems was 30.1%. In the AIS based study conducted by Nowak et al. (2015) in a group of 133 female public health students, 51% of the respondents had insomnia [40].
One of the factors that significantly influences sleep is shift work and studying, as pointed out by Ohayon (2001), who indicates that people working in shifts or night modes are more likely to struggle with sleep disorders [41]. A study by Wolinska (2020) comparing employed and unemployed individuals did not show any correlation between shift work and insomnia, but, interestingly, proved that insomnia was more common in unemployed ones (p ≤ 0.001) [42].
Our study revealed a statistically significant relationship between the presence of insomnia and depression in a group of 18-25 year olds. Similarly, based on their meta-analysis, Hertenstein et al. (2019) demonstrated that insomnia is a predictor of depression and anxiety disorders [21]. Similar results were reported by Benbir et al. (2015). They found that 13% of the subjects suffering from insomnia exhibited symptoms of depression or other mental disorders [43]. In turn, Levenson et al. (2015) observed a marked worsening of insomnia in patients with depression [44].
Our study showed no relationship between insomnia and the time spent in front of the screen of electronic devices and exposure to blue light emitted from these media. A different conclusion was reached by Exelmans et al. (2016), who proved a significant impact of using smartphones in the evening on the occurrence of insomnia. The effects of this in the case of older individuals were different from those in younger ones, but in both groups, using such devices at bedtime resulted in insomnia and the feeling of fatigue during the day [19]. This problem was noted by Chellappa et al. (2013), who provided evidence that exposure to blue-saturated light in a not very brightly lit room has a significantly negative effect on sleep. Hence, care should be taken to ensure that working in front of electronic devices during evening and night time is done with the light on [17]. On the other hand, Benbir et al. (2015) confirmed a relationship between insomnia and watching TV for 6-8 hours a day in 18.4% of the respondents [43].