The proliferation of new technologies and cyberspace including personal computers, tablets and mobile phones has led to changes in people’s habits and behavior [1]. The revolution of information and communication technologies has not only changed the methods of communication and access to information, but also had led to the emergence of new phobias and psychological disorders [2]. One of these technologies that is more common is mobile phones. Studies have shown that mobile phones, in addition to their benefits, may have cause some problems such as habitual checking [3] and excessive usage [4]. Nomophobia (No-mobile-phone-phobia) is a disorder that is caused by the use of smartphones, which is defined as the fear of not having a working mobile phone [5]. Nomophobia, as a modern age phobia, was emerged through the interaction of people and communication technologies, especially smartphones [6]. It is a state of anxiety and stress that occurs if a person does not have access to a smartphone [7]. It has been reported that nomophobia is related to internet use disorder and mobile phone addiction. Internet use disorder is characterized by spending too much time on the Internet and being unable to disconnect from it, which may disrupt the normal daily life and generate social conflicts [8]. Mobile phone addiction is defined as a loss of control over smartphone use that interferes with other activities [9], while nomophobia refers to traumatic fear of not having access to smartphone [2]. According to studies, the prevalence of nomophobia among adolescent students is about 70% [7, 10-13]. The pervasiveness of such devices can lead to mental health problems such as panic disorder [5], social anxiety disorder [1], loneliness, problematic internet use, social media excessive usage [14], internet addiction [7], impaired social and marital relationships as well as medical problems such as exposure to radiation, screen dermatitis, tumors, and infertility. This study aims to assess the validity and reliability of the Persian version of Nomophobia Questionnaire (NMP-Q) developed by Yildirim and Correia (2015).

Participants and procedure
Participants were 283 college students with a Mean±SD age of 22±2.48 years ranging from 18 to 30 years (92 males and 191 females) who were selected by a cluster sampling method. First, the main version of NMP-Q was translated to Persian by three MA students in psychology and its content validity was then evaluated by two members of psychology faculty. Next, an expert (MA in English Language) translated it back to English, and the quality of translation was conformed. To collect data, the initial Persian NMP-Q as well as the Cellphone Overuse Scale (COS) were distributed among participants. To evaluate the test-retest reliability of the Persian NMP-Q, 30 samples were randomly selected from among the participants to fill the questionnaire after two weeks. Collected data were analyzed in SPSS v. 20 and LISREL v.8 applications using Pearson correlation test, Cronbach’s alpha, and confirmatory factor analysis. 
Instruments
The NMP-Q has 20 questions and 4 subscales which are: not being able to access information (items 1-4), giving up convenience (items 5-9), not being able to communicate (items 10-15), and losing connectedness (items 16-20). The responses are rated on a scale from 1 to 7 to measure the intensity of nomophobia. Higher scores indicate severe nomophobia. This questionnaire was developed by Yildirim and Correia (2015) and has high validity (Cronbach alpha= 0.94 for overall questionnaire and 0.923, 0.874, 0.827, and 0.814 for each four subscale). The concurrent reliability of this questionnaire was reported 0.71. It has been translated to Spanish and Italian languages [6].
The COS was developed by Genaro et al. (2007) and has 23 items that measure overuse of cell-phone. This scale was prepared based on 10 criteria of Diagnostic and Statistical Manual of Mental Disorders. This scale has no subscale and its items are rated on a six-point Likert scale [15]. The Persian version COS was prepared by Mohamadian et al. (2012) with 21 items. They reported the validity of Persian COS using Cronbach’s alpha as 0.903, and its test-retest reliability was 0.71 which was significant (P<0.01) [16].

Of 283 participants, 65.9% were female and 33.1% were male; 71.2% were single and 26.7% were married. In order to evaluate the internal consistency, Cronbach’s alpha was used. Cronbach’s alpha for overall questionnaire was obtained 0.921, while for not being able to communicate, losing connectedness, not being able to access information and giving up convenience was 0.885, 0.882, 0.748, and 0.788, respectively, which shows the high internal consistency of the Persian NMP-Q (Table 1).



To calculate the correlation between the items and the total score, Pearson correlation test was used. The results showed significant correlation (P<0.001). The correlation test between the factors and the total score showed that the highest correlation (r=0.82) was related to “not being able to communicate” (first Factor) and “losing connectedness” (second factor). The lowest correlation (r=0.43) was related to “losing connectedness” (second factor) and “not being able to access information” (third factor). Moreover, the correlation test between subscales and the total score showed a coefficient of 0.82, 0.76, 0.74, and 0.87 for the first to forth subscales, respectively. As show on Table 1, all results were significant (P<0.001).
Confirmatory factor analysis was used to evaluate the factor structure of the questionnaire. For this purpose, Bartlett’s test was used. Moreover, the Kaiser–Meyer–Olkin (KMO) measure of sampling adequacy was examined to assess the sampling adequacy during the analysis. Bartlett’s test of sphericity result (2908.7) was significant (P<0.01) and the KMO index was obtained 0.915, which is greater than the minimum acceptable value. Thus, the results of these tests indicate that the questionnaire is appropriate for factor analysis. Moreover, the goodness-of-fit indices (DF=164, chi-square=593.7, and RSEMA=0.097) were acceptable. Factor analysis results for each factor are presented in Table 1. The minimum factor loading was related to the item no.3 belonged to the third factor, and the highest factor loading was related to the item no.18 belonged to the second factor. The factor loading of all items was significant (P<0.05). Based on the results, the factor analysis model of the questionnaire had good fit.
Furthermore, to evaluate the concurrent validity of the Persian NMP-Q, COS questionnaire was used. Results showed a correlation coefficient of 0.59 (P<0.001), indicating a convergent correlation between two questionnaires. The results of test-retest reliability showed a correlation coefficient of r= 0.81 for overall questionnaire, and 0.86, 0.88, 0,88, and 0,89 for each four subscales which were significant (P<0.001).

The results of this study showed that the Persian NMP-Q has acceptable validity and reliability for measuring Iranian population. The main NMP-Q has four subscales which were confirmed in the Persian version after conducting confirmatory factor analysis. Cronbach’s alpha of the main version (α=0.945) is close to that of Persian version (α=0.921). The results of correlation test showed acceptable test-retest reliability of the Persian version (r= 0.81, P<0.001). Moreover, examining the correlation between the Persian NMP-Q and COS, results showed acceptable concurrent validity of the Persian NMP-Q (r= 0.59, P<0.001). These findings are consistent with those of Bragazzi et al. [8] who validated the Italian version of NMP-Q and reported a Cronbach’s alpha of 0.95. In their study, all four subscales of questionnaire were confirmed in the Italian version. Our results are also consistent with those of González et al. [2] the NMP-Q was translated to Spanish and then validated. In their study, a Cronbach’s alpha of 0.95 was obtained for the overall scale and all subscales of the main version were confirmed. 

This study obtained its ethical approval from the Ethics Committee of Iran University of Medical Sciences (Code: IR.IUMS.REC.1396.30448). All ethical principles are considered in this article. The participants were informed about the purpose of the research and its implementation stages. They were also assured about the confidentiality of their information and were free to leave the study whenever they wished, and if desired, the research results would be available to them.

This study was supported by the Research Department of the Faculty of Behavioral Sciences and Mental Health (Tehran Psychiatric Institute) of Iran University of Medical Sciences.

Conceptualization: All authors; Methodology: Ahmad Ashouri, Mohsen Alizadeh; Data collection: Mohsen Alizadeh, Mohsen Hassani, Gohar Miyabandi; Data analysis, drafting: All Authors; Editing and finalizing: Mohsen Alizadeh; Project management: Ahmad Ashouri.

The authors declare no conflict of interest. 
 

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