For contemporary societies where the prevalence for mental disorders seems to compromise quality of life and economic prosperity, not only through direct costs of health and social services but also due to lost employment and productivity, the implementation of mental health promotion (MHP) programs is imperative as they may become instrumental for addressing such issues . The Ottawa Charter, as a declaration statement and an institutional context, developed by the World Health Organization (WHO) in 1986, highlighted the goals of MHP and identified improvement of health policies as one of its first-line aims 
. In the context of these premises, a MHP strategy can be advanced in every possible human setting by building healthy public policies, creating supportive environments, strengthening community action, developing relevant to mental health personal skills and in general reorienting health services to early detection of disorders and promotion of health and well-being [1, 2]. Similarly, in the European Union, the so-called Green Paper was formulated in 2005, constituting a declaration document of proposals for the establishment of an inclusive strategy on MHP across the European countries .
It is widely recognized that promoting mental health and addressing mental ill health can be endeavored at different levels, taking into consideration individual, family, community and social determinants of mental health, and strengthening protective factors while reducing risk factors .
At a community and group level, the degree of knowledge and understanding about the nature of mental health and mental illness has been identified as a key element for changing health policies and practices . Therefore, human settings such as schools and workplaces are considered crucial for MHP education. In schools in particular, an inclusive intervention program can increase social competencies, improve resilience and reduce bullying, anxiety and depressive symptoms [5, 6]. In addition, promoting mental health in children, adolescents and parent populations may improve their mental health through the development of particular skills relevant to each group [7, 8].
With regard to work environments, it is widely known that poor working conditions may lead to poor mental health, and increase sick leave rates and costs. Thus, interventions aiming at strengthening individual capacity and reducing stressors in the work setting are expected to improve health and support economic development .
It is also noted that the use of alcohol or any psychoactive substances constitute important MHP challenges to be addressed within different populations, not only in the high risk groups but also in early prevention programs, as for example in preschool children [3, 8]. Targeting high-risk populations for ill health is a common methodological practice in MHP. Thus, in old age for instance, involving changes in the individual's functional capacity, social participation and mental health, supportive interventions aiming at improving and sustaining mental well-being in older patients are highly recommended . In overall high-risk populations such as people with restricted socioeconomic resources, those experiencing job loss and unemployment, migrants and refugees or other marginalized groups constitute groups in need of supportive MHP interventions .
Besides MHP educational and training interventions for the enhancement of mental health in general, specifically addressing discriminatory attitudes and misconceptions about mental illness within the community is an important target of MHP actions. When negative and biased opinions are expressed within a particular social group, it is important to address such issues by means of MHP educational interventions at the level of community so that professionals and various groups of influence in the community may develop informed positive attitudes about mental illness . In such cases, MHP programs may provide knowledge to key agents in the community as to recognize mental health issues, improving personal coping skills and becoming trained to initiate effective community action against ill health [11–13].
However, a major issue in policymaking regarding MHP programs concerns the effectiveness of interventions and evidence-based outcomes taking into consideration that examples of effective MHP activities are few and far between . Tang et al.  proposed an interesting four-level typology of evidence in the field of health promotion. According to this typology, the first two types, types A and B, presuppose that what works and how it works in an intervention are known, while in the other two types, types C and D, what works is known but how it works is not known. Repeatability claims to be universal in type C, but limited in type D. Most interventions in the field of health promotion would be categorized within the lower levels of C and D evidence, while A and B levels are scarce. It is noteworthy that MHP actions take always place in specific and dynamic contexts, wherein sociocultural, political, human and coincidental or other factors may interact. In this sense, positive effects of a certain MHP intervention cannot be considered easily replicable at any time and any place.
In order to clarify the issue of how a MHP intervention works, distinction of the intervention's components and knowledge on causal links between them and the outcome measures are needed. In the absence of such knowledge, most of the MHP intervention programs can be classified as providing types C and D level of evidence.
Although scarce, examples of evidence based effective MHP educational programs in the literature do exist, a few of which are mentioned below. (1) An educational campaign carried out by Wolff et al.  on a target population neighboring supported houses for people with mental illness. The intervention led to a decrease of fearful and rejecting attitudes and increase of social contact with staff and patients. These findings suggest that the educational campaign exerted its effect on attitudes by encouraging contact with patients. (2) In New Zealand, Vaughan  reported on a nationwide MHP campaign, including education and training, providing evidence that awareness among the general public, as well as attitudes and behaviors towards people with experience of mental illness can be improved. (3) In a multisite European study (The European Early Promotion Project) , training was offered to a quasiexperimental group of primary health care professionals and its effects were assessed: it was found that recipients tended to improve their knowledge, perceived self-efficacy and ability to identify families in need. (4) Considering the dimension of cost benefits, Zechmeister et al.,  extensively reviewed the existing research on the cost effectiveness of MHP and prevention interventions. They suggest that most favorable results belong, almost exclusively, to early intervention programs for children and adolescents, which thus seem worth financing.
In the present study we investigated the immediate or direct effects of a three-semester MHP intervention. The specific MHP educational program rests on providing scientific knowledge and information to key agents in the community regarding mental illness and mental health issues [11–13]. It includes addressing discriminatory attitudes and misconceptions about mental illness in the community and enhancing self-assessed mental health as they constitute important targets of MHP . Therefore, the following hypotheses were tested in relation to this three-semester MHP program: (a) if the participants' opinions towards mental illness and the mentally ill individuals would become more favorable after receiving the MHP educational program, (b) if the participants' self-reported mental health would become more positive after intervention, and (c) if there would be any differences or changes in the variables of opinions and self-reported health according to sociodemographic variables.