Depression is one of the most widespread diseases across the world and a major factor in problems of mental health (Sarokhani et al.

, 2013).  The issue of students’ mental health is a global problem that covers all developed and non-developed societies, both modern and traditional (Bayram & Bilgel, 2008).  During their academic life young people face many contradictions and obligations to succeed, especially at university (Arslan, Ayranci, Unsal & Arslants, 2009).

 Also, university students should make the efforts to embrace new experiences and changes in social aspects, and in behavioral, emotional, academic and economic situations (Ginwright & James, 2002).  Therefore, it is important to understand concerns regarding students’ mental health. The mental health problems of students are widely studied at different educational levels, such as college and university (Bayram & Bilgel, 2008).  A number of studies have indicated a high prevalence of mental health problems among students, including depression, compared to the rest of the population (Yusoff et al., 2013).  More importantly, recent studies in this area indicate that the psychological and mental problems of students continue to increase (Field, Diego, Pelaez, Deeds & Delgado, 2012).  For example, in the United States a national survey in 2005 mentioned that 86% of university counseling centers noted an increase in serious mental health and psychological problems among university students (Gallagher, Weaver-Graham & Tylor, 2005).

One of the most prevalent problems of mental health is depression, which is a serious health problem among the student population (Ibrahim, Kelly, Adams & Glazebrook, 2013). Moreover, depression has a significant impact on academic performance, academic satisfaction and academic achievement (Arslan et al., 2009).  A study by Wechsler, Lee, Kuo and Lee (2000) reported that students with symptoms of depression achieve lower grades and are less active in the classroom relative to students who do not have these symptoms.  The findings show that depression is a serious problem that requires psychological support for the majority of students.Prevalence of depression among students  Depression is one of the most prevalent problems in the mental health of students at different educational levels, such as high school, college and university (Arslan et al., 2009). Previous studies have proposed that psychological morbidity, particularly depression, is a common disorder among students (Adewuya, Ola, Olutayo, Mapayi & Oginni, 2006; Dahlin et al.

, 2005). Studies of psychological problems encountered by counseling centers revealed that depression was one of the five most common problems among college students.  They highlighted that depression accounted for 39% of problems, a higher rate than anxiety, problems with romantic relationships, and the self-esteem of students across different settings (Erdur-Baker, Aberson, Borrow & Draper, 2006; Green, Lowry & Kopta, 2003). Recently, many studies have been carried out on the rate of depression among students (Chen et al., 2013). They report that depression is a widespread problem and continues to increase in the student population (Sarokhani et al., 2013).

 For instance, one study stated that the rate of depression varied from 10% to 40% among university students in Turkey (Ustun & Kessler, 2002).  In addition, Green, Lowry and Kopta (2003) indicated that adult students reported higher levels of symptoms of depression compared to the adult non-student population.  Other studies in this area have also found that the symptoms of depression range from 27% and over, among students and these symptoms represent the most common problems encountered by university counseling centers (Mobley, 2008).  Although the prevalence of depression in the student population compared to the general population has not been well researched. A number of studies have looked at the rate of depression among particular groups of students. A systematic review of published studies, from January 1980 to May 2005 about the rate of depression in Canadian and US medical students, reported higher levels of depression in the student population compared to the general population (Dyrbye, Thomas & Shanafelt, 2006).  However, based on this study we cannot conclude that the prevalence of depression in students is higher than the general population.  This is because the study used only Canadian and US medical students, and the sample of this systematic review only included 40 studies during the period January 1980 to May 2005.

 Another recent systematic review reported that depression in university students is much higher compared to the general population (Ibrahim et al., 2013).  Additionally, Dahlin, Joneborg and Runeson (2005) found that the rates of depression in the general population were lower relative to that of medical students at the Karolinska Institute in Sweden. Likewise, a more recent study by Haldorsen, Bak, Dissing and Petersson (2014) found that the prevalence of depression among Danish medical students was remarkably higher than the Danish population as a whole. A Nigerian study by Adewuya et al. (2006), about the prevalence of depression among university students, found the rate of depression among Nigerian students was only 2.7%.

This is much lower compared to the rate of depression among Nigerian outpatients visiting general clinics (25%), or compared to an older population sample (over 60 years) (18.3%) in western Nigeria (Uwakwe, 2000).  Another study (Rosal et al., 1997) stated that the level of depression in the general population was approximately the same as medical students at the University of Massachusetts.  Additionally, a recent study on depression in Chinese university students by Chen and his colleagues (2013) concluded that the prevalence of depression was similar to that of the non-student population in the Chinese city of Harbin.

 Over recent decades, a large number of studies have been conducted on the rate of depression in medical students (Dyrbye, Thomas & Ahanafelt, 2005).  Recent studies (Sidana et al., 2012; Dahlin et al., 2005; Dyrbye et al., 2006) have reported that the rate of depression in medical students is higher than that of the general population.  In the literature it can be clearly seen that medical students, as subjects, cover most of the studies about the prevalence of student depression.

 Studies highlight that the rate of depression in medical students shows a higher score relative to students of other degrees (Yusoff et al., 2013).  Studies about the prevalence of psychological distress among medical students indicated that the rate of depression students at different medical institutions in different countries ranges between 7% and 26% (Sidana et al., 2012), whereas at 39% among Indian medical students it is a serious problem for students in India (Vaidya & Mulgaonkar, 2012, cited in Sidana et al., 2012).  A study in the United Kingdom reported that approximately one-third of medical students (first-year) have mental health problems of depression and anxiety (Guthrie et al., 1995 cited in Dyrbye, Thomas & Shanafelt, 2005).

 Other studies have mentioned that 12% of medical students in the United Students have serious symptoms of depression measured by DSM III standard (Zoccolillo, Murphy & Wetzel, 1986).  Compared to law students, Canadian medical students recorded higher rates of depression (Dahlin et al., 2005).