Positive psychology is a new branch of psychology the goal of which is to examine psychological capacities and powers instead of psychopathology. The fundamental belief in positive psychology is that positive, measurable features can be protective against risky adverse events. Psychologists interested in this field have focused their attention on the potential sources of positive emotions such as happiness [1].

It is suggested that happiness can be accompanied by consequences such as success in marriage, relationship, and career; and more income and health and longevity. There are, of course, some views which indicate that more successful people feel happier in their lives as a result of their success. However, in a review study conducted in 2005, the presented mental model showed that happiness was indeed the cause of success, not its effect [2].

Happiness has been attributed to various factors, one of which is individual personality differences. The results of studies suggest that the underlying personality structure determines people’s tendency for happiness. It seems that in extrovert people, happiness is achieved through self-expression and social behavior [3].

In studies in which happiness are evaluated subjectively by asking individuals through self-report questionnaire, for expressing happiness, a person presents a cognitive and affective assessment of their entire being. In these studies, in empirical research, three components have been identified: positive affection, negative affection, and life satisfaction [4]. Therefore, a person’s expressed happiness consists of cognitive and emotional dimensions. The emotional dimension of happiness can be affected by various factors. One of these factors can be emotional intelligence. Emotional intelligence is defined as a talent for understanding, feeling, and using these feelings as a basis to influence human communications. In fact, it is one’s ability to recognize emotions to motivate himself/herself and to manage the emotions in communicating with people. In other words, it is one’s ability to monitor the emotions of themselves and other people in order to use this information to differentiate between people and guide their thoughts and actions [5]. In general, there is a significant relationship between emotional intelligence and psychological, psychosomatic, and physical health. However, more studies are required to clarify the direct and indirect relationships between emotional intelligence and health [6]. Higher emotional intelligence as a feature can cause an individual to be able to deal with acute daily stresses and perceived chronic stress and to be even happier [7].

It is important to note that emotional intelligence and intelligence quotient are not against each other, but are different. High-intelligence individuals may have high or low emotional intelligence and vice versa [7].

The study of emotional intelligence has been the subject of many studies in different target groups including students. Increasing usage of therapeutic facilities, moving toward patient-centered care and increasing the importance of clinical competencies require a wider range of interpersonal and intrapersonal skills in the medical professions. It is even recommended that emotional intelligence is studied as a useful potential structure in assessing the desirable cognitive and non-cognitive abilities of people working in healthcare [8].

A study on the emotional intelligence of the first-year medical students showed that the emotional intelligence of these students decreased over time and it had some fluctuations. However, the clinical impact of such changes was not studied [9]. Although most medical students begin their professional education with idealism, enthusiasm, and attention to humanity, they realize during the course that they are drawn away from their path. For many, challenges including balancing their happiness, social responsibility and professional (or clinical) training can be very frustrating. The medical students’ health can greatly affect the health of society due to their important role in preserving and promoting it. We aimed to study the relationship between emotional intelligence and happiness among the students of Shiraz Medical School. Shiraz University of Medical Sciences is a high rank training center in the south of Iran, with more than seventy years of medical education experience. The result of this study can be a way to help students with physical and mental health problems.

Considering the existence of an entrance test in Iran, entering the medical field needs a higher academic level than other disciplines. As a result, the intelligence rate of medical students is higher than that of ordinary people.

On the other hand, emotional intelligence is another factor which affects people’s health [10]. As Post [11] stated in his article that happiness is another effective factor in the health of the individuals.

This research was a descriptive and cross-sectional study. The target population of this study was the students who entered Shiraz Medical School and its international branch from September 2014 to September 2017.

The sample size was calculated 285 students regarding type I error equal to 5%, confidence interval equal to 95%, and response distribution equal to 50%. Three hundred students (150 men and 150 women; 225 students studying in Shiraz Medical School and 75 students studying in its international branch) were selected as study’s sample by systematic sampling [12]. The data gathering tools were Oxford Happiness and Shering’s Emotional Intelligence Questionnaires. As to grading of Happiness Questionnaire which has 29 four-choice questions, the first choice has 0 point, choice 2 has 1 point, choice 3 has 2 points, and choice 4 has 3 points. Finally, every individual has a grade from 0 to 87 and the higher grade shows more happiness. Reliability and validity of this test was evaluated and Cronbach’s α was calculated 0.901 [13]. Shering’s Emotional Intelligence Questionnaire consists of 33 five-choice questions. Grading is done by 5-point scale from 1 to 5. The sum of the grades that every individual gains makes up for his or her total grade. Shering’s Emotional Intelligence Questionnaire assesses five scales of emotional intelligence consisting of self-awareness, self-control, self-arousal, sympathy, and social skills. Reliability and validity of this questionnaire have been assessed and chronbach’s α was calculated 0.85 [14].

Researchers attended the classes. According to the random codes which were chosen before, the questionnaires were filled out as self-report and in varying times by test subjects and their student number was used as their code. Descriptive statistics were used to describe the data and analytic statistics, such as chi-square and t-test were applied to analyze the data. Moreover, for ethical consideration, it is noted in the beginning of the questionnaire that the test subjects have contributed in this study freely and voluntarily and filling out this questionnaire means that they have free and informed consent.

In this study, the relationship between emotional intelligence and happiness in medical students was evaluated. There was a statistically significant positive correlation between happiness and emotional intelligence. This indicates that emotional intelligence predicts happiness, and this finding is consistent with the studies by Hasan Nia et al. [15], Tuzhandehjani et al. [16], and Seyed Reza and Soleimani [17]. Emotional intelligence in happiness is a key element and important. Emotional intelligence theorists believe that emotional intelligence leads to increased happiness and high emotional intelligence is a protective mental factor [18].

There was a significant negative relationship between the participants’ age and happiness (aesthetic feeling). As the participant’s age increases, the aesthetic sense of happiness decreases. There are different views on the relationship between these two variables. According to Morgan et al. [19], happiness has a downward trend to age in developing countries which is consistent with the results of this study. On the other hand, happiness is proportional to age in developed countries, which is not consistent with the results of our research [19].

Also, the strongest predictor of level of happiness in this study population was personality types (introverted and extroverted). The mean of happiness was higher in extroverted people. However, other researches had variable results in this regard; for example, Snel [20] showed that outward personality was a factor for happiness and they were related. It seems that the reason for this association is that outward people have more social activity [21]. Lu and Shih [22] found that there was not any relationship between extroversion and happiness. As people who are less happy are more prone to illnesses [23]. A family physicians can find out people who are introverted and pay more attention to them and prevent their illnesses, so we can reduce health costs.

There was a positive significant relationship between emotional intelligence and perceived health level and students who had higher emotional intelligence feel healthier. Several other studies have shown that there is a significant and positive relationship between emotional intelligence and both general and mental health [24-28]. Several studies on students have shown that information and skills training for students can increase emotional intelligence and, thus, lead to better educational outcomes [29,30].

It is noteworthy that this study is a cross-sectional study and more prospective studies are suggested for exploring the risk factors and confirming the relationship. However, in this study, happiness, emotional intelligence, health status, stress level, and type of personality of students were simultaneously evaluated along with demographic factors, to understand which factor can explain the changes in the happiness level in regression model.

In conclusion, in the studied population, emotional intelligence has a significant positive relationship with happiness. Furthermore, students with higher emotional intelligence felt healthier. Because of the importance of mental and physical health in medical students, so the predictive role of emotional intelligence should be considered by authorities.

In this study students who had extroverted personality were significantly happier than students with introverted personality. It is suggested that the students who had introverted personality be more supported to increase their level of happiness. For better understanding of factors in which effect on happiness of medical students, replication of this study in other countries and with prospective design is highly suggested.