Depression is the most widespread disease 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 societies, both traditional and modern (Bayram, 2008). During their academic life young people face many contradictions and obligations to succeed, especially at university (Arslan, Ayranci, Unsal, 2009). Also, university students should make the efforts to embrace new experiences in their lives 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 schools, college and university (Bayram&Bilgel, 2008). Number of studies have indicated a high prevalence of mental health problems among university 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 85% of university counseling centers noted an increase in serious psychological and mental health problems among university students (Gallagher, Weaver-Graham & Tylor, 2005). One of the most prevalent problems of mental health is depression, which is the serious health problem among the student population (Ibrahim, Kelly, Adams &Glazebrook, 2013). Moreover, depression has a significant impact on academic grades, 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 show these symptoms. The findings show that depression is a very serious problem that requires psychological support for 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, in colleges 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 said that depression was one of the 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 increased from 10% to 40% among university students in Turkey (Ustun& Kessler, 2002). In addition, Green, Lowry and Kopta (2003) revealed 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 of depression encountered by university counseling centers (Mobley, 2008). 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 say 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 study 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 as 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 higher than the Danish population as a whole. Student gender and depression It can be expected that, in general, the prevalence of depression in females is more than that of males in the general population (Piccinell& Wilkinson, 2000). Nelon-Hoeksema, Larson and Grayson (1999), in their study on gender differences of depression, reported that the reasons for these differences of these symptoms are not clear, whereas gender differences in depressive disorders are well documented in most of the studies. More specifically, a twin study in this area has shown that there is no relationship between gender difference in depression and genetic risk, and that factors are more likely to correlate to environmental aspects, namely family history, social support, economic situation and life events (Tenant, 2002). In reviewing the findings of gender differences of the prevalence of depression in students, the empirical studies have revealed different results. The majority of these studies have found that gender is a major factor with regard to depression among students. Several recent studies about have proven that there was no difference in the rates of depression in male and female students. That means that gender does not play a role in the rate of depression. For example, a recent study (Byaram&Bilgel, 2008) on the prevalence of depression in Turkey has proven that there was no difference in the score rate with regard to depression in male and female students. Other recent studies by Arslan et al. (2009) and Rosal,Ockene, Barrett and Hebert (1997), on the prevalence of depression in university students, have shown that there was no significant difference between the sexes. Additionally, a more recent study (Yusoff et al., 2013), on the prevalence and factors related to depression in 743 Malaysian university students, indicated that male and female students show nearly same degree of depression, and difference in gender was not a significant factor. Similarly, findings from samples of Turkish university students using “Beck Depression Inventory” and “Public Health questionnaire” recorded the rates of depression between male and female students (Bostanci et al., 2005). Also, a more recent study by Haldorsen et al. (2014) of Danish medical students showed that female students recorded slightly higher rates compared to male students, but these differences between the sexes were not significant. However, a large number of studies about students’ symptoms of depression reveal that male and female students do have different rates of depression. Most of these studies indicate that the rate of depression is higher in female students compared to male students, but the reason for this was not identified. In a recent study by Adewuya et al. (2006), on the prevalence of depression among Nigerian students using the interview instrument Mini International Neuropsychiatric, there was a significant difference between the sexes in rates of depression among university students, with rates in female students two times more than male students. Moreover, in the most recent systematic review by Ibrahim et al. (2013), using the results of 24 recent articles from 1990 to 2010 about depression in university students, a majority of these articles (16) reported gender differences in the prevalence of depression among University students. Fifteen of these articles concluded that the rate of depression in female students was higher as compare to male students; only one article reported a higher rate for men. In addition, Dahlin et al. (2005) and Ceyhan, Ceyhan and Kurtyilmaz (2009) pointed out that female students had a more risk of depression compared to male students. Eisenberg, Gollust,Golberstein and Hefner (2007) observed the same result as they mentioned that symptoms of depression were higher in female undergraduate students as compare to male undergraduate students. Student’s age and depression In terms of student’s age, some studies in particular looked at the relationship between age and depression in students. A study on depression among Malaysian university students concluded that the prevalence of depression was higher in older students compared to younger students (Shamsuddin et al., 2013). This result also was emphasized in other studies; senior university students have greater rates of depression relative to beginner students (Bostanci et al., 2005;Khawaja, 2008). In contrast, studies in this area (Bayram and Bilgel, 2008; Tomoda et al., 2000) have shown that students in their last year of university have lower levels of depression compared to new students. It is hypothesized that this difference in the above findings might be because of using different samples of students, and different methods of measuring depression. It is somewhat surprising that no relationship was found in this condition. One study showed that the level of depression in older students is nearly the same as younger students (Lester, 1990). This would indicate there is no significant relationship between a student’s age and the prevalence of depression. Depression and academic performanceA number of studies have proven that symptoms of depression affect student’s performance and achievement at university, college and school (Stark , 1994, cited in Shamsuddin et al., 2013). Findings in this area show that academic tasks cause a high risk of mental health problems, especially depression in students (Ibrahim et al., 2013; Sharif et al., 2011). A Turkish study found that depressed students have a poor academic performance as compare to students who do not show symptoms of depression (Bostanci et al., 2005). Owens, Stevenson, Hadwin and Norgate (2012), on anxiety and depression on academic performance among students in the UK, found that depression has a negative relationship with academic performance. They investigated that a higher level of depression was associated with lower academic performance. Another study about the impact of depression on academic performance among undergraduate students revealed that depression has a strong and a negative relationship with academic performance. This robust and risky relationship includes a number of negative consequences for students (Hysenbagasi et al., 2005). Similarly, a recent study by Ceyhan et al. (2009), on depression in university students, showed that students who have a poor academic achievement demonstrated considerably greater depressive symptoms as compare to students who indicated a high level of academic achievement. It also should be considered that student’s depression is a serious risk to academic impairment, which continues and is increased by depression during academic life (Heiligenstien& Guenther, 1996). For this reason it is assumed that poor academic success or performance is one of the main reasons of depression among students (Baker &Siryk, 1984). However, it is not easy to decide if depression is a result of a low level of academic achievement or vice versa. Depression can have a negative impact on cognitive functioning and this can impact negatively on academic performance or achievement (Turner, Thompson, Huber &Arif, 2012). Common causes of depression among students The distinct causes of depression among students have not been investigated, particularly in the previously done studies. It is important to remember that the above studies have revealed high rates in the prevalence of depression (from 5% to 30%) in students across the whole world (Ibrahim & Kelly, 2011). The large variation in this percentage has not been mentioned, but it might be said that this is because the studies were performed in different types of populations, societies and cultural backgrounds (Bayram&Bilgel, 2008;Dahlinat al., 2005). Another factor in this large variation may be due to the studies using different methodologies to diagnose this problem among university students (Ovuga, Boardman & Wasserman, 2006). In the literature, studies have showed different factors of depression among students, but there are some common causes of depression among students. This part of the review will look at common factors in many of the studies about the prevalence of depression in students in their academic career. The first serious cause associated with the depression among students is socio-economic status. A less number of studies have investigated the effect of socio-economic factors on depression in the student population (Ibrahim et al., 2013). Student’s socio-economic level has been shown to play a prominent role in the symptoms of depression in students (Sareen, Afifi, McMillan , 2001). A large cross-national (from 23 countries) study (Steptoe, Tsuda, Tanaka & Wardle, 2007) on the relationship between symptoms of depression and socio-economic background of university students revealed that family and personal income level, parental education and family wealth, contributed to depression in students. Similarly, data from an analysis of Egyptian studies on the relationship between socio-economic status and depression among undergraduate students showed that socio-economic background associated negatively with symptoms of depression among students. This study concluded that students from families with a lower level of income and parental occupation as compare to others have a tendency towards depression (Ibrahim et al., 2013). Moreover, it might be explained that some students from rural areas move away and leave their families while at university, and this might cause some problems for some students. Studies also show that students who have higher socio-economic position such as a high level of social class, an educated background and economic situation, are more likely to have a sense of control. This sense of control can provide students better protection against mental health diseases, namely depression, associated with moving to a university environment (Lanchman& Weaver, 1998). Additionally, the educational level of student’s parents could play role in depression related with the university environment of students. For example, Ibrahim et al. (2013) found that students with less educated family are 50% to 60% more likely to suffer from problems of depression as compare to highly educated families (father and mother). It is also proved that the father’s occupation has an effect on depression in students. For instance, Ibrahim and Kelly (2011) found that students whose father had a professional job are 60% more likely to obtain depressive disorders compared to students whose father was not a skilled worker. The second most common cause, reported as a serious factor for the rate of depression in students, is living away from home or transition to new environment, such as university and college. For some students, separation from home or family might be a reason of psychological diseases, especially depression. This is due to difficulties associated with living in a new and different environment at university or college without social support (Asyan, Thompson , 2001). It was also found that students who live at home with their families are not likely to be affected by depression because their families provide them more support and enhanced protection against academic stress (Christie, Munro & Retting, 2002). Another problem with accommodation is that students who live alone face problems without social support, especially international students. A study by Haldorsen et al. (2014) showed that students dealing with social problems and psychological distress have a higher rate of the symptoms of depression as compare to students living with their own families. The above evidence shows that students, who live with their family and partners and have the social support to cope with their problems, have a better way of living without depression. Although the transition to college and university is a successful step, and it is a good opportunity for students to have a good future, in poor countries it might cause some students who go to university some social and psychological problems, including depression. For example,Adewuya and his colleagues (2006) revealed that symptoms of depression in Nigerian students could be caused by poor academic conditions, overcrowded classrooms,a poor quality of accommodation, and a lack of learning materials. An important finding mentioned in the recent study of Haldorsen et al. (2014) found that the stress factors of students have significant association with symptoms of depression. In the previous study Haldorsen et al. (2014) concluded that high stress in students led to high symptoms of depression. Similarly,Bayram and Bilgel (2008) emphasized the same relationship between depression, stress and anxiety. The third main cause of depression among students is study’s satisfaction. That means that students who are not satisfied with their course of study have higher rate of depression than students who are satisfied (Bayram&Bilgel, 2008). A possible interpretation for this finding might be the student’s lack of interest and motivation in their major, because sometimes the student’s parents choose the subject for study (Chen et al., 2013). Another recent study showed that students who are content with their education are less likely to suffer from depression and anxiety (Dahlin et al., 2005). Interestingly, another cause of depression in school and college age students is body size or body weight. Depression associated to body size has been investigated by many studies (Granberg, Simons, Gibbons &Melby, 2008). There is evidence of no relationship between body weight and psychological distress in university students. For example, a study by Granberg and his colleagues (2008) on the relationship between depression and body size among 343 African-American middle-school females, showed no link between symptoms of depression and weight. That means that an unhealthy weight did not cause more symptoms of depression among those female students. The authors clarified that this finding may be due to the belief that African-American girls are more likely to overestimate their weight. Additionally, some studies highlighted that obesity or being overweight has a positive correlation with depression in adolescents in the United States (Jorm et al., 2003). Jorm and his colleagues also revealed that these studies also looked at gender differences in overweight adults. They found that female adults in the United States were highly depressed as compare to male adults. A possible interpretation of this phenomenon may indicate the findings that boys are less likely to overestimate their weight, and they do not weigh enough, whereas mostly girls overestimate their weight (Strauss,1999). From the above evidence, it may be true that adults and younger students who have a healthy or normal weight are less depressed as compare to adult students who have an unhealthy or abnormal weight. Indeed, adult female students are more likely to show symptoms of depression. Furthermore, Ceyhan and Kurtyilmaz (2009) found that students who are satisfied with their body looks are less depressed as compare to students who are not happy with their body looks. Serious consequences It is clear that depression has negative consequence for students as individuals in society. Few studies have been performed about the effect of depression on student’s personal ability and academic career. It is suggested that depression can cause many mental and physical disorders, which are big problems for students who make up an important part of the population in the community (Bayram, 2008). Hysenbegasi et al. (2005) revealed that depression might cause problems for the future occupations of studentsby delaying access or creating difficulties in choosing a career. Another study by Field et al. (2012) reported that depression brings many mental problems, which cause psychological, social and physical problems for students during and after their academic life. It is believed the major hurdles in student’s depression include poor self-assessment, lack of pleasure and interest in everyday life(Arslan et al., 2009). Additionally, this disorder has many negative effects related with personal, cognitive, and emotional problems, notably, decision making and problems of time management (Chen et al., 2013); poor academic achievement and lower level of exam performance (Hysenbegasi et al., 2005); less attention and drug abuse; over consumption of alcohol and higher levels of smoking in adults and university students (Yusoff et al., 2013); and negative effects on everyday work and achievements (Sobocki, Lekander, Borgstrom, Dtrom&Runeson, 2007). Most importantly, the most serious problem of depression is the threat of suicide in students. An earlier study on suicide in students showed that depression is the most prevalent reason of suicide attempts among university students (Eisenberg et al., 2007).The study revealed that 2.7% of depressed students tried to commit suicide, while 9.5% to 10% had suicidal thoughts (Dahlin et al., 2005; Kisch, Leino& Silverman, 2005).