Extended Abstract
1. Introduction
Advances in the electronic communication technologies, despite a lot of benefits, have exposed the youth to some threats such as sexting. Among American teenagers aged 12-13 years, 68% have mobile phones and 23% smart phones and their most common usage is sending and receiving SMS, so that the average SMS transmission among them could rise up to 60 per day. Teenagers may be at particular risks and serious harms related to these new technologies. In particular, using a mobile phone to send or receive naked or half-naked or sexually explicit content in recent years has got public health attention. 
Sexting for the first time entered English language in 2011 and officially recorded in the Oxford Dictionary. In Iran, the use of mobile phones among teenagers is high. The average hours of mobile phone use among high school students in Tehran was 5.99 hours per week, and 1.8% of users use mobile phones for more than 16 hours a week. Of mobile phone owners, 17.9% sent over 101 text messages per week and 23.1% received over 101 text messages per week. The content of these messages in 10.7% of cases was sexual contents or images. Studies revealed teenagers who do sexting are more likely to become victims of siberian bullying, depression or suicide. Also, sexting was associated with vaginal, anal and oral sex, as well as unprotected sex in adolescents. This study aimed to determine the youth access to mobile phone and the prevalence of sexting in high school students in Rafsanjan.

2. Method
 The study was a cross-sectional local survey of 944 female and male high school students in Rafsanjan City, Iran. Inclusion criteria consisted of being Iranian and under the age of 18. The presence of a known psychological disorder, as well as unwillingness to participate in research at any time, led to the exclusion from the study. All high schools in Rafsanjan were considered as research environment. We used cluster sampling method in 16 public schools, 6 special schools, 13 technical schools and 11 private schools, with a total of 10000 students in Rafsanjan City. In each category for girls and boys, a special school, a public school, a technical, and a private school were randomly selected. Calculating the sample size in each school was based on the number of students in that school and with the proportion of 10% of the total number of school students. 
The questionnaires were completed by the study samples. The counselors or school deputies who had previously been informed about the appropriate sampling method collaborated in data gathering. Samples were allowed to complete the questionnaires in a private environment. To protect the privacy, the questionnaires after being completed by students, were dropped in a box. Before delivering the questionnaire, the students were assured of the confidentiality of their information. The survey tool was a questionnaire of texting and sexting quantity and quality consisted of demographic characteristics, information about having a mobile phone and how to use it to send messages, access the Internet and social networks, and sexting. The present questionnaire was inspired by similar research studies. The obtained data were entered the SPSS version 16 and analyzed using Chi square and t-test.

3. Results
Out of 994 samples, 10.9% did not access to mobile phones. About 62.7% of samples had smart phones and internet access via mobile phones. Regarding the use of social networks, 129 (13.7%) of the total research samples were mobile Internet users and 62.7% of all research samples had access to other services such as Viber, WhatsApp and Instagram. Out of total samples, 270 (28.6%) people sent less than 10 messages daily, while 182 (19.3%) sent more than 50 messages per day. In the last six months, 34.7% of samples had sent sext and 15.7% had received sext. 
In case of receiving sext, 663 (77.8%) people said that they quickly deleted the message, 54 (6.3%) forwarded it to others, and 135 (15.8%) of them saved and sometimes saw it. There was an association between students' gender with receiving (P<0.0001) and sending (P<0.0001) sext, so that girls sent and received sexts more than boys. There was no significant statistical difference between the four types of schools regarding students’ sexting, although students in technical schools were more likely to do sexting than three other types of schools. There was a statistical significant relationship between sending (P<0.0001) and receiving sext (P<0.0001) and the total number of texting per day.

4. Discussion
 In the present study, the majority of Rafsanjan high school students had access to mobile phones and just 10.9% had not. This amount of access to mobile phones is much higher than students from the United States and equates to almost all other Iranian reported cases. About three-fourths of the entire research units could use other social networks through mobile phones, which confirms that most students have smart phones, while this proportion is 23% among American students. It is clear that increasing access to social networks in the form of a mobile phone, which is usually a personal device and is subject to little parental control, can be potentially harmful to the cyber-security of children and young people. 
That is why the access to smart phones among children and teens is limited in many countries, and unfortunately, having this device among many of our teens in our country has become a logical need or demand. About one-fifth of the samples sent more than 50 messages per day. Particularly, as the number of messages increases every day, the likelihood of sexting increases; this high volume of text messaging among students should be considered. More than a third of the students reported having sexting in the last six months. 
It should be noted that sexting in previous investigations is directly related to the sexual activity among adolescents. Therefore, this high prevalence of sexting can represent a significant amount of sexual activity among adolescents. Studies show that these interactions in this age of ignorance and impotence of adolescents can expose them to problems such as sexually transmitted diseases specially HIV/AIDS as well as unwanted pregnancy and social and behavioral problems and reveals the need for parents supervision and plan for parenting education.

Ethical Considerations
Compliance with ethical guidelines
This study was approved by the Ethics Committee of Rafsanjan University of Medical Sciences (code: 93590). Necessary permissions were obtained from the Education Center of Rafsanjan. Also consent was obtained from students.

Funding
This study received financial support from Rafsanjan University of Medical Sciences. It is an approved research project. 

Authors contributions
All authors contributed in preparing this article.

Conflict of interest
The authors declared no conflict of interest.

Acknowledgements
Authors would like to thank authorities of study high schools and parents of students for their valuable cooperation.