In recent years, research on positive psychology has emerged highlighting the role of positive psychological variables in making life more successful, improving human functioning, and increasing happiness [1]. Broadly, the literature has distinguished between two dimensions of "wellbeing" or "positive mental health" [2, 3]: hedonic or subjective well-being, which emphasizes constructs such as positive feelings, positive affect, subjective well-being, life satisfaction or happiness; and eudemonic or psychological well-being tradition, which accentuates positive psychological functioning and human development (i.e., engagement, fulfilment, sense of meaning, social wellbeing).

Among constructs related to positive well-being, research into happiness has increased considerably over the past forty years. Some of the most widely accepted definitions of happiness [1, 4–6] agree that subjective well-being is defined as the evaluative reaction of a person to his/her life and it can be divided into a cognitive component (cognitive evaluation of life satisfaction) and an affective component (emotional aspects of the construct, such as happiness). Therefore, subjective positive well-being is a broad category of phenomena, whereas happiness specifically represents the affective evaluation of one's life, although they are often regarded as synonymous [7].

Broadly, there is accumulating evidence (cross-sectional, longitudinal and experimental research) that positive well-being is associated with many resources valued by society, such as healthy behaviours, lower delinquent activity, higher incomes, superior mental health, a higher education, a long life, better performance ratings at work, an improved social and personal functioning, lower heavy Internet and game use, etc. [7–15]. In short, the results reveal that happiness has multiple benefits, being associated with and precedes numerous successful outcomes, as well as behaviours paralleling success. Furthermore, the evidence suggests that positive affect--the hallmark of well-being--may be the cause of many of the desirable characteristics, resources, and successes correlated with happiness [7].

Specifically, the direct effect of well-being on future health has been proposed to be mediated through two pathways: the association between positive psychological states, such as happiness, and a lower perceived stress and/or favourable biological responses to stress (including low cortisol levels, reduced cardiovascular disease risk, faster cardiovascular stress recovery, reduced inflammation, and resilience to infection) and the relationship with healthy lifestyles and prudent health behaviours that reduce long-term risk of disease development [16].

As regards stress, in general empirical evidence suggests that there are marked associations between positive psychological states, such as happiness, and perceived stress, indicating that there was an inverse relationship between these variables [14]. At the biological level, cortisol output has been consistently shown to be lower (or at least a more flexible response) among individuals reporting positive affect, and favourable associations with heart rate, blood pressure, and inflammatory markers such as interleukin-6 have also been described [17].

Regarding healthy lifestyles and prudent health behaviours, previous studies have found that there is a significant association between happiness and health outcomes, such as exercising regularly or higher levels of physical exercise, not smoking or less cigarette use, less alcohol intake, higher sleep quality and quantity, and prudent diet [18–21]. Therefore, happy individuals are less likely to engage in a variety of harmful and unhealthy behaviours, including smoking, unhealthy eating, and abuse of drugs and alcohol [22]. Thus, positive affect might benefit health by indirect relations to health promoting activities.

Results of studies concerning the association between obesity and happiness or well-being are conflicting. Some of them did not find evidence that increased weight impairs happiness [19, 23]. However, a study found that a significant U-shaped trend in the association between body mass index categories (underweight, normal, overweight and obesity) and depression, which could be considered as the opposite extreme of happiness [24].

In spite of these data, following Grant et al. [16] or Steptoe et al. [11] the association between positive affect and healthy behaviour choices are quite mixed and some results have been inconsistent [19, 25–27]. Even less is known about associations between well-being and other health behaviours such as dietary choice.

Furthermore, despite there is a substantial number of cross-cultural studies about well-being and happiness [16, 28, 29], none of them has studied the relationship between happiness and health outcomes in Latin American college samples previously.

Therefore the main aim of this study was to confirm associations between subjective happiness and perceived stress and the relationship between happiness and healthy lifestyles and prudent health behaviours, such as physical activity, smoking, and alcohol consumption, and test relationships with other behaviours, specifically with three aspects of food choice (fruit/vegetables, breakfast and lunch intake) and with body index mass categories following the World Health Organization recommendations.

We hypothesized that happiness would be positively associated with lower scores on perceived stress, supporting the idea that favourable response to stress (including biological correlates and perceived stress) is related to positive psychological states. We also expected a significant relationship between happiness and some healthy behaviours (a better diet quality, daily exercise and the lack of any drug taking). Both outcomes would give partial support to the idea of that mediation of happiness in reducing long-term risk of disease development through both pathways also appear in Latin American samples.

The main objective of the study was to confirm associations between subjective happiness (one of the construct related to positive psychological states and well-being) and favourable health outcomes in a Latin American sample. Traditionally, it has been purposed that this relationship takes place through two pathways: its relationship with favourable biological responses to stress and its connection with healthy lifestyles and prudent health behaviours. On the one hand, we pretended to give support to the relationship between happiness and lower scores on perceived stress, as a correlate of favourable psychobiological responses to stress. On the other hand, we tried to find some evidence of the association of happiness with some health behaviours, as an expression of healthy lifestyles and prudent health behaviours.

A substantial number of young adults in this study reported very high happiness, with 30.80% of the total sample saying that they were very happy with their lives (scores of 6 or above in a 7-point Likert scale). Even more, if we considered people over the mean score, the rate was higher, approximately 50%. This data are consistent with those indicating that 23% (range = 12-27%) of young adults reports being very satisfied with their life as a whole (very positive well-being) across culture [16] or other study showing an average level of "very happy" people of 27.5% (range = 8-47%). In general, all these studies found that subjective well-being or happiness is higher in Western countries, followed by countries from Eastern Europe and finally Asian countries [16, 29, 36].

Our results indicated that being very happy was more common among female. Although gender effect has previously presented some ambiguity, in general, it appears that women tend to report higher happiness levels than men [16, 37]. Anyway, it seems to be evidence of paradoxical women's declining relative wellbeing across demographic group and industrialized countries over recent decades in comparison with the opposite effect among men [38]. Furthermore, some studies display that there is a specific difference in the gender distribution of well-being across world regions, with women reporting greater levels of well-being on average in Asian countries, but lower levels than men in the Western countries [16]. Anyway, genetic studies do not find any age effect [39, 40].

Referring to the relationship between age and happiness, we found that happiness was higher in the younger group. This data is consistent with those by Dear et al. [37] that found that life satisfaction was higher in young adults than in the middle -aged or elderly or Bartels et al. [39] who reported a small but significant negative effect of age on mean levels of subjective well-being. Although some studies have found the opposite age effect, highlighting that aging is a preventative factor of depressive state and/or felling of unhappiness [19], or have not showed any age effect [40], this apparent contradiction has been clarified recently. Some studies have proved that there are non-linear effects, but well-being is U-shaped over the life cycle. In general, these studies show that lower levels of happiness are among the 35 and 62 years of age -middle age- across gender and countries [41]. Furthermore, this work confirmed this result for a large, heterogeneous sample of countries (72 developed and developing countries), taking into account potential cohort effects. This finding is also coherent with our data, corresponding with some point of the increasing left tail of the U-shaped distribution.

The hypothesis related to the association between happiness and perceived stress was largely confirmed (in both univariate and multivariate analyses), indicating that participants who perceived higher levels of stress in ordinary circumstances and during tests situations reported being less happy than those with lower levels of stress. These results are in line with previous evidence showing that there is an inverse relationship between happiness with perceived stress by means of self-reported measures [14, 17]. So, Schiffrin et al. [14] found that both self-reported variables were inverse associated by means of a correlational study with college students, whereas Mikolajczak et al. [17] also found the same effect plus a relationship between subjective happiness and a biological marker of psychological and physical health status, the cortisol awakening response flexibility. This study is consistent with previous studies [14] suggesting that one of the main practical implications of this finding is that interventions designed to increase happiness might benefit from the inclusion of activities to manage and cope with stress and that this sort of interventions should also utilize state measures of happiness that are sensitive to increases in happiness that may occur as a result of the intervention.

The second main hypothesis of the study was partially confirmed, in that happiness was positively associated with most of the prudent health behaviours except alcohol consumption, and other drug uses. Effects were positive and significant, but moderate for daily breakfast, daily lunch, daily fruit and vegetables intake and daily physical activity, as well as they were negative for prescriptive and unprescriptive tranquilizers intake and obesity. When the calculations were adjusted by means of the multivariated analysis, obesity, daily breakfast and unprescriptive tranquilizers intake were no longer statistically associated with subjective happiness, but smoking emerged as a new significant predictor of happiness to be added to the previous mentioned variables. In general, our results therefore add to the limited data currently available relating well-being and happiness with prudent health behaviour in Latin American countries.

Overall, our results are consistent with other studies that pointed out that life satisfaction is positively associated with most of the prudent health behaviours across culturally diverse countries, with effects strong for psychical exercise, intermediate for fruit intake and lower but significant for cigarette smoking and dietary fat avoidance [16]. In addition to this, other studies have also found an association of high self-rated health with more physically active, more sleep, less likely to be overweight, lower scores on loneliness, shyness and hopelessness, and higher on self-rated happiness [12] and between positive lifestyle changes such as increasing physical activity levels and increase in fruit and vegetable consumption and positive changes in mental health (peacefulness and happiness) [42].

Regarding physical activity, they are also coherent with a study showing that exercise participation is associated with higher levels of life satisfaction and happiness, and that both variables appeared to be mediated by genetic factors [21] or with another one highlighting a inversely association between jogging and other types of psychical activity in leisure time with stress and life dissatisfaction [43]. Most of these studies recommend that increased well-being should be a key argument in future campaigns for increased leisure-time physical activity.

Previous research relating dietary quality with positive well-being has been inconsistent, at least in Western countries, regarding daily breakfast and snacks intake [16, 19]. Other previous works reported a significant relationship with fruits and vegetables and limiting fat intake [16, 42]. Our findings give a stronger support to this relationship related to daily intake of lunch and fruit and vegetables, and a significant, but lower support to the association with daily breakfast intake. Therefore, our findings are consistent with these previous studies.

Regarding obesity, our data showed a low but significantly positive relationships between obesity and a lower happiness. Although previous studies indicated contradictory outcomes regarding the association between obesity or BMI categories and happiness or well-being [19, 23], however, our outcome is consistent with those by de Wit et al. [24] showing a significant U-shaped trend in the association between body mass index categories (underweight, normal, overweight and obesity) and depression, which could be considered as the opposite extreme of happiness. Probably, the lack of agreement could be made clear because of most studies focused on linear- (positive, negative) or no trends in the association between obesity and depression/happiness, whereas a u-shaped association is a better explanation.

Our results showed that happiness was moderately and negatively related to prescriptive tranquilizers intake, and lower but also significantly with unprescriptive tranquilizers intake. This finding is in line with the controversy about the use of the psychotropic drugs labelled as happiness pills or "happy pills" during the last half 60 years. In this sense, some authors have highlighted that "happiness pills" has become a "national nightmare" [44]; the problem of iatrogenic addiction in the age of happiness pills as 'Botox' for the mind [45] or the unhappy saga of happy pills [46].

Surprisingly, we also found a low positive association between happiness and smoking by means of the multivariate analysis, whereas we did not find any relationship between happiness and other drugs consumptions, such as alcohol intake, marihuana consumption, etc. The results about the association between positive affect and healthy behaviour have been quite have been inconsistent [19, 25–27]. So, on the one hand, some studies have found a relationship of well-being with no smoking or less cigarette use [11, 16, 22, 47]; with less alcohol intake [27] and with no smoking nor abuse of drugs or alcohol [22]. On the other hand, other works did not find this relationship between neither smoking nor alcohol intake and happiness [19]. Even, other studies found a positive relationship between alcohol intake and higher well-being among university students [26] or a U-shaped relationship between well-being and alcohol consumption, whereby well-being was lower both in abstainers and in heavy users [37]. Thus, positive affect might benefit health by indirect relations to health promoting activities, although the relationship seems to be more complex than expected. In example, a tentative explanation for the inconsistency about the relationship between smoking and well-being has been that smoking might partly be a consequence of negative affective states, while stopping smoking or reducing cigarette consumption leads to enhanced well-being and happiness [48].

To sum up, our findings are mainly consistent with previous studies, indicating that healthy lifestyles and prudent health behaviours are positively associated with happiness. Furthermore, studies have pointed out that both genes and environment play important roles in the associations between well-being and health [49].

This study has a number of strength, including a large homogeneous sample, uniform measures of health behaviours, a standard assessment of happiness and the novelty of including a Latin American sample. There are also several limitations. This study was cross-sectional, so causal relationships cannot be drawn. The study was carried out with students from a public university of one country from Latin America, and inclusion of other centres could have resulted in different effects. The association between happiness and food might be moderated by income. Despite the fact that participants belonged to a broad variety of municipalities from Chile with different level of incomes following the Chilean National Institute of Statistics, there was no data on participants' income. Furthermore, our university students sample are not representative of Chilean young adults in general, and the rate of happiness and health behaviours may be different in other sector of the population. Students were tested here by means of self-report items and scales, and more refined assessments with objective verification would have been desirable.

Nevertheless, the results add to the literature in documenting associations between positive well-being/happiness and a range of behaviours and emotional responses relevant to health in a different cultural group. The findings of this study are consistent with the notion that health behaviours and perceived stress account in part for the relationship between positive psychological states and good health, providing support to the double pathway in which well-being seems to have an effect on health outcomes. It also underscore the importance of that some healthy behaviours and person's cognitive appraisal of stress are integrated into their lifestyle for college students. Additionally, highlight the importance of taking into account these variables in the design of strategies to promote health education in university setting. Finally, our findings pointed out the extent of happiness in an emerging country such as Chile, which is comparable to that of western countries belonging to the so-called "western culture" (thus despite economic and other cultural differences).