Mental health and happiness play a crucial role in providing opportunities for individual and social improvement [1-3]. Consequently, they can prepare grounds for national improvement and blooming of communities, including the scientific and academic communities, especially the students and ensure their dynamism and efficiency. Obviously, mental health and happiness which are necessary components of student life have direct effects in these selected strata's learning and increase their scientific awareness [4-6].
World Health Organization (WHO) has defined mental health as a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity [7-9].
Mental health is the ability to communicate harmoniously, change and modify the personal and social environment and to solve personal desires and controversies in a logical, fair and suitable way [10-12]. Mental health provides the person with the ability to disclose their thoughts and have a healthy interaction with the environment .
As it can be inferred from this definition, mental health can be considered the ability to avoid anxiety and disability symptoms, constructive communication with others and the ability to confront the pressures in life. Happiness is also considered an important part of living quality . Happiness is a combination of the presence of positive emotions and lack of negative emotions and satisfaction with one's life .
The person with higher levels of happiness, feels more relaxed and secured, makes decisions easier, works more efficiently and cooperates more, lives a healthy and more energetic life and finally has a more satisfactory life . Schwartz and Stark (1991) believe that happy people are the ones with an optimistic and happy orientation, that is, they process and interpret information in such a way to lead to their happiness .
A review of the literature on mental health and happiness indicates how important this issue is. Therefore, significant positive relationships have been reported between mental health and spiritual intelligence , mental health and emotional intelligence components , mental health and effectiveness of educational activities  and mental health and job satisfaction . In addition, a significant positive relationship is also observed between happiness and spiritual health , happiness and organizational atmosphere , happiness and job satisfaction  and happiness and educational background and gender .
According to the aforementioned points and the significance of this subject, this study investigated the relationship between mental health and happiness in students and aimed at answering the question whether mental health was significantly related to happiness in students.
Considering the nature of the current study, this was a descriptive study following a correlational approach. The statistical population included all the students of educational sciences (bachelors and masters) in the University of Sistan and Baluchestan, which was a total number of 400 students.
A total number of 196 subjects were selected by simple random sampling and based on Morgan's table. After the data were collected, the incomplete questionnaires (15 copies) were excluded and the analysis was done using the remaining 181 questionnaires.
Two questionnaires were used in this study for data collection. The first was the General Health Questionnaire (GHQ) that includes 28 questions and was introduced by Goldberg (1979) with a scale of 0-3. The reliability of this questionnaire in the present study was calculated (0.77).
The second one was the happiness questionnaire proposed by Argyle and Crossland (1989). Each part of this scale is assigned four options (phrases) in the scale of 0-3 which indicates the degree of happiness. The subjects should select one of the options as the answer. The reliability of this questionnaire in the present study was 0.94. SPSS version 19 was used for data analysis.
1. There is a significant relationship between mental health and happiness of students.
2. There is a significant difference in mental health of students in terms of their marital status.
3. There is a significant difference in happiness of students in terms of their marital status.
Table (1) shows that the correlation coefficient between mental health and happiness is r=0.47 which is calculated at the confidence level of 99 percent (P<0.01). That is, there is a significant positive relationship between mental health and happiness of the students.
Table (2) indicates that the mean and standard deviation of single students are 71.70 and 17.36, respectively. Moreover, the mean and standard deviation of married students are 67.27 and 21.82, respectively. This difference is not significant (P>0.05) at t=0.080 with a degree of freedom of 179 at confidence level of 95 percent. Therefore, it can be concluded that there is no significant difference in happiness of students in terms of their marital status.
The present study was conducted with the aim of investigating the relationship between mental health and happiness of students of educational sciences in the University of Sistan and Baluchestan. The results of Pearson's correlation coefficient showed that there is a significant positive relationship between mental health and happiness of the students. This is consistent with findings of the study by Mahdinejad (2012), Rezapour (2011) and Salarifar et al. (2008). Furthermore, the results of the independent t-test showed that there is no significant difference between mental health and happiness of students in terms of their marital status. This is consistent with findings of Yaghoobi (2010) and Chen et al. (2013). However, findings of this study are not consistent with those of Alipour and Aarab Sheibani (2011).