social, and economic burdens (Ayittey et al., 2020; Webham et al., 2020) . More specifically, these policies force residents to stay indoors and limit physical contact among individuals for substantial amounts of time. With such prolonged stays indoors and without face-to-face contact with family and friends, the human nature of social interaction is violated and has interrupted individuals' daily life routine alongside increased fear of infection, financial stress, and other psychologically stressful factors (Brooks et al., 2020; Lee et al., 2018) .
With the prolonged enforced home stay, individuals have no choice but to shift living focus from social activities to indoor activities and may end up engaging more in sedentary behaviors than normal (e.g., internet and social media use; Chen et al., accepted). One reason for increased internet and social media use is that individuals want to obtain information concerning COVID-19. Indeed, a recent Chinese study found that more than 80% of its surveyed 1304 participants reported staying at home 20 to 24 hours a day since the outbreak of COVID-19 due to closures of schools and businesses . The same study also found that more than 90% of the participants obtained COVID-19 information from internet and they were keen to know more about COVID-19, including the COVID-19 transmission route, the medication and vaccine availability and effectiveness, travel advice, overseas COVID-19 control experiences, the number of confirmed cases with locations, COVID-19 prevention advice, tailored-made information for different populations (e.g., children and individuals with chronic illnesses), and detailed information on COVID-19 infection symptoms . Similar online behavior was observed during the Middle East respiratory syndrome coronavirus (MERS-CoV) outbreak, where disease-related online information searches increased in Korea (Shin et al., 2016) .
Unfortunately, disease information obtained from the internet or social media may not always be correct. A recent study assessing knowledge and perceptions of COVID-19 from the general public in the United States and United Kingdom reported that participants believed J o u r n a l P r e -p r o o f Journal Pre-proof some misconceptions and falsehoods that had circulated on social media (Geldsetzer, 2020).
Moreover, was reported that nearly 200 Iranians died and more than 1,000 were poisoned by overconsumption in alcohol because they believed in the rumors on social media claiming that drinking alcohol could cure COVID-19 (Aksut, 2020) . The aforementioned tragedy indicates that COVID-19 misunderstanding due to incorrect social media information may lead to psychological distress and inappropriate behaviors. Although numerous mental health professionals and public health experts claim the need to consider psychological distress among different populations during the COVID-19 outbreak (Asmundson and Taylor, 2020; Bao et al., 2020; Lima et al., 2020; Pakpour et al., 2020a Pakpour et al., , 2020b Shigemura et al., 2020) , to the best of the present authors' knowledge, only three studies have collected empirical data examining this issue (Ahorsu et al., 202a; Xiao et al., 2020) . Therefore, collecting empirical data to study psychological distress of a population (such as the young adults in the present sample) during COVID-19 outbreak is vitally important, and will provide meaningful information for healthcare providers to design appropriate campaigns to promote public mental health. More specifically, problematic social media use, fear of COVID-19, COVID-19 misunderstanding, psychological distress, and insomnia are all relevant areas where information should be collected and investigated. Therefore, the present study thus proposed a potential psychopathology mechanism to explain psychological distress among the Iranian young adults during the COVID-19 public health crisis. It was hypothesized that (i) higher problematic social media use would be associated with the greater fear of COVID-19 and COVID-19 misunderstanding; (ii) greater fear of COVID-19 and COVID-19 misunderstanding would be associated with the higher levels of psychological distress; (iii) greater fear of COVID-19 and COVID-19 misunderstanding would be associated with more severe insomnia; (iv) fear of COVID-19 and COVID-19 misunderstanding would be mediators in the association between problematic social media J o u r n a l P r e -p r o o f Journal Pre-proof use and psychological distress; and (v) fear of COVID-19 and COVID-19 misunderstanding would be mediators in the association between problematic social media use and insomnia.
The study was approved by the Ethics Committee of the Qazvin University of Medical Sciences (IR.QUMS.REC.1398.375). A non-probability sampling strategy was used in the administration of an online survey. Online survey software (Google Forms) was utilized to carry out the survey. The study sample was invited via social media, online advertising, community websites, and student's online newsletters. Individuals were eligible to participate if they were 18 years or older, able to read and complete an online consent form and survey in Persian/Farsi, possessing a smartphone, and having access to the internet.
After providing informed consent (online), participants completed online self-report measures of problematic social media use and provided demographic information at an initial data collection stage (T1). One week later, follow-up measures of fear and misunderstanding concerning COVID-19 were completed by the same participants (T2). Finally, two weeks after initial assessment (T3), the same participants were asked to self-report on insomnia and psychological distress.
14-item instrument rated on a four-point Likert-type scale (score from 0 to 3), was used to assess the psychological distress. The HADS item scores were summed, with a higher score indicating a greater level of psychological distress. The psychometric properties (including construct validity, concurrent validity, test-retest reliability, and internal consistency) of the Persian HADS have been found satisfactory in prior research . The internal consistency of the HADS in the present study was very good (α = 0.81).
Journal Pre-proof 2.2.2. Insomnia. The Insomnia Severity Index (ISI), a seven-item scale rated on a five-point Likert-type scale (score from 0 to 4), was used to assess the severity of insomnia.
The ISI item scores were summed, with a higher score indicating a greater level of insomnia.
The psychometric properties (including construct validity, concurrent validity, test-retest reliability, and internal consistency) of the Persian ISI have been found satisfactory in prior research . The internal consistency of the ISI in the present study was very good (α = 0.86).
six-item instrument rated on a five-point Likert-type scale (score from 1 to 5), was used to assess the severity of problematic social media use. The BSMAS item scores were summed, with a higher score indicating a greater level of being at risk of social media addiction. The psychometric properties (including construct validity, concurrent validity, test-retest reliability, and internal consistency) of the Persian BSMAS have been found satisfactory in prior research . The internal consistency of the BSMAS in the present study was very good (α = 0.88).
The Fear of COVID-19 Scale (FCV-19S), a seven-item instrument rated on a five-point Likert-type scale (score from 1 to 5), was used to assess the fear level of COVID-19. The FCV-19S item scores were summed, with a higher score indicating a greater level of COVID-19 fear. The psychometric properties (including construct validity, concurrent validity, test-retest reliability, and internal consistency) of the Persian FCV-19S have been found satisfactory in prior research (Ahorsu et al., 2020b) . The internal consistency
The sample was relatively young (mean age = 26.24 years [SD±7.41]) with fewer males (n = 628; 41.7%). Most of the participants had completed higher education (n = 861; 79.9% with a college or above degree) and had no comorbidities (n = 905; 83.9%) ( Table 1) . Table 2 reports the mean (and SD) of the participants' levels in psychological distress, problematic social media use, fear of COVID-19, COVID-19 misunderstanding, and insomnia. The aforementioned variables were mutually and significantly correlated (all p-values < 0.01).
Moreover, psychological distress was moderately correlated with all the other factors (r = 0.294 to 0.475) ( Table 2) .
(Insert Tables 1 and 2 here) Table 3 showed that problematic social media use was significantly associated with Table 3 here)
The present study is the first to demonstrate the temporal associations between Because the mortality rate of COVID-19 is not low and the individuals recovered from COVID-19 are likely to have health consequences (Baud et al., 2020) , general populations have reason to feel fear of COVID19 Xiao et al., 2020) . However, the present study showed that such fear may be magnified when the individuals received negative COVID-19 information from social media. From the present findings, higher levels of problematic social media use were associated with a higher level of fear of COVID-19 one week later. Individuals with greater problematic social media use are likely to be exposed more to COVID-19 information than those with less problematic social media use. Given that a substantial amount of misinformation and misconception can be found in social media (Geldsetzer, 2020) , individuals with greater problematic social media use are therefore more likely to have greater COVID-19 misunderstanding.
The fear of COVID-19 and COVID-19 misunderstanding were found to be associated with psychological distress in the present study. This finding was expected because fear is usually an initial psychological response for individuals to respond to threat, and this can allow the individuals take action to protect themselves (Lang et al., 2000) . However, when an individual cannot tackle the fear for a specific period of time, prolonged fear may subsequently lead to the development other types of psychological distress, such anxiety and depression (Kuriyama et al., 2010) . This human biopsychological mechanism also helps explain why fear of COVID-19 appeared to be associated with the development of J o u r n a l P r e -p r o o f Journal Pre-proof psychological distress in the present study's sample. Regarding COVID-19 misunderstanding, it is likely that when individuals receive substantial amounts of misinformation and misconceptions concerning COVID-19 (Geldsetzer, 2020) , their uneasiness is increased and consequently reflected by psychological distress.
The fear of COVID-19 but not COVID-19 misunderstanding was found to be a factor that was associated with insomnia in the present study. With substantial evidence showing that individuals with fear have sleep problems (Kuriyama et al., 2020) , it is reasonable that fear of COVID-19 was associated with insomnia. That is, when an individual worries and fears COVID-19, the individual's brain is stimulated and excited (Kuriyama et al., 2010) . Therefore, the individual cannot take rest and develops insomnia. This finding may supplement the finding from Xiao et al. (2020) that individuals during the COVID-19
pandemic have sleep problems. Although COVID-19 misunderstanding was not directly associated with insomnia, COVID-19 misunderstanding may be indirectly associated with insomnia via psychological distress. More specifically, psychological distress was found to be associated with insomnia in previous research (Belleville and Morin, 2008) . Therefore, diminishing COVID-19 misunderstanding may also help overcome insomnia among the general population. However, stronger evidence is needed concerning causal relationships between the variables examined in the present study.
There are some limitations in the present study. First, it is unclear how, where, and what COVID-19 information the participants obtained. Moreover, the items used in the present study to assess COVID-19 misunderstanding did not cover all the misconceptions on COVID-19. Therefore, impacts of specific misinformation cannot be determined and the COVID-19 misunderstanding found in the present study may be underestimated. Second, a convenience sampling utilizing an online survey was used to collect data among Iranians.
Therefore, the generalizability of the present study's findings is restricted (i.e., the present J o u r n a l P r e -p r o o f Journal Pre-proof study's sample does not represent all Iranian young adults and the study's results cannot necessarily be generalized to Western populations. Third, although the present study intended to collect longitudinal data across three time points with an interval of one week apart, the temporal effects might be trivial because it is hard for an individual to change the mental capacity in such short time periods. However, in order to provide immediate and timely information on psychological distress during the COVID-19 pandemic, the present authors reasoned that the optimal method to understand temporal effects was to use short interval periods. Nevertheless, the present study cannot provide strong evidence in terms of causality given the following issues: (i) the lack of information on potential confounders (i.e., financial status and wellbeing, changes in living arrangements, changes in lifestyle) and (ii) the lack of baseline assessments concerning psychological distress and insomnia. Finally, all the data were self-report and the common method biases from collecting such data cannot be avoided.
For example, participants may have responded with socially desirable answers and reported less problematic social media use and better health.
Due to the pressure of the COVID-19 outbreak, general populations are highly likely to develop psychological distress and insomnia. The elevated psychological distress may be triggered by fear of COVID-19 and COVID-19 misunderstanding. Insomnia may be induced by fear of COVID-19. Therefore, in addition to developing appropriate health and social policies to help minimize the spread of COVID-19, healthcare providers should also design 