A total of 3668 publications were initially identified. Table 1 provides a summary of the 11 studies that met the inclusion criteria. The majority of studies were quantitative (n = 8) rather than qualitative (n = 3). There were no randomised-controlled trials in the identified studies, with the majority being cross-sectional (n = 8). Two were classified as prospective. One of these was a study using cross-sectional sample data over a 22 year period  and the other states it is prospective without providing details of waves of measurement time . Whilst one study is classified as longitudinal, it only covers a single Rugby League season with multiple measurement periods within the season .
The sample sizes in the studies that met the inclusion criteria ranged from 14 to 19,842 participants. The majority of studies (n = 8) had over 100 participants. The majority of studies were conducted in Australia (n = 3) and United Kingdom (n = 3), followed by United States of America (n = 2), Belgium (n = 2), and Germany (n = 1). The age of study participants was generally adult exclusively (n = 7) with four studies including older adolescents too. Nearly all (n = 8) included both males and females. The three Australian studies focused exclusively on males [25, 28] or females .
Most studies scored highly on the modified Downs and Black scale of study quality (median 71 percent; range 44–93 percent). Those studies scored above the median value (higher quality) were all cross-sectional quantitative studies [10, 24, 29–31]. None of the studies of higher quality incorporated a theoretical approach. Within the studies of higher quality, there was no consistency regarding the components of sport and other PA investigated. Instead, these included: sport at least monthly , club sport , leisure time sport , team sport , and sport . As a consequence of the varied study designs, low number of studies, and differing aspects of sport investigated, there was no clear distinction between the key findings of the higher and lower ranked studies in terms of the psychological and social health benefits of participation in sport.
Thirteen different psychosocial health aspects were identified in the ten studies (Table 2). The most common positive health benefit was improved well-being [24, 25, 28, 32], followed by reduced stress [23, 28, 31], reduced distress [23, 29, 32] and increased social functioning [10, 24] and vitality [10, 24].
The definitions and measurement of sport participation varied considerably. Several studies classified sport participation by frequency only [24, 26, 29, 31], whilst others classified measurement by favourite sport , club sport , team sport  or context of participation such as competitive versus recreational . The types of sport activities were generally not defined, however Eime et al.  defined club participants as participating in netball and/or tennis, and King et al.  measured stress and recovery in Rugby League. The measurement was often in binary terms where those participating in sport were compared to those participating in other activities or to those not participating in any activity. Sport was not always the focus of each paper and in some instances sport was measured as one context of PA participation .
Half of the studies incorporated a theoretical perspective. Two incorporated a Grounded theory theoretical perspective to their enquiry [25, 27], whilst others utilised specific theories such as the Mindful Movement theory and Self-Determination theory to explain behaviours.
Few differences were evident between the conclusions of studies of higher and lower quality or of different study design. Although the total number of studies reviewed was relatively small, there were some differences in the reported health outcomes associated with different contexts of participation. Therefore the following presents a summary of the psychological and social health benefits of participation in sport according to the different contexts of sport participation/definition.
Sport participation in general
A study by Asztalos et al.  compared sport to other forms of PA with regard to mental health. As these authors explain, the relationship between physical activity and mental health may change across different domains of activity. In their study Asztalos et al. examined the associations between participation in five domains of PA: housework leisure active transportation, biking to/from work, walking to/from work, and sports participation . The aspects of mental health measured were perceived stress and psychological distress. The mean frequency of sports participation in the sample of 1919 adults was once per week, averaging 2.75 hours/week. Sport participation was based upon this mean, and specifically the adults had to participate weekly for at least 2.75 hours. Whilst the data was controlled for gender, age and occupation, they did not do so for level of PA. Nonetheless, sports participation was the only type of PA inversely associated with both stress and distress. On the other hand, housework was associated with more stress and distress for women with blue-collar jobs. Biking to work was associated with more stress for men with blue-collar jobs. The authors provided some reasons why they believe that sport participation, and not other types of activities, had better mental health outcomes. They explained that sport represents a chosen leisure-time activity and aims for recreation, enjoyment and social interaction which promotes well-being. Furthermore, these improved levels of well-being are not associated with PA that implies compulsion which to an extent, housework and active transport do. Similarly, Harmer et al.  investigated PA in different domains of sport, walking and domestic PA. They found significant benefits of participation on reduced psychological distress for all types of activity with participants only needing a minimum of 20 per week to have significant differences in mental health measures . The strongest effects were observed for sport participation. A dose–response pattern was reported, which demonstrated greater risk reduction with higher volume and/or intensity of participation.
Club sport participation
A recent study investigated sport participation more specifically. Eime et al.  hypothesised that sports club participants would have improved health related quality of life (HRQoL) and life satisfaction given the social nature of their participation, compared to more individual PA activities such as walking and going to the gymnasium . These authors also compared these contexts of participation with a normative reference group of participants, which measured the same health aspects. Even after adjusting for differences in levels of PA, club participants had better physical role functioning, vitality, social functioning, mental health and life satisfaction than gymnasium and walking participants. These results support the notion that participation in a socially engaged manner can contribute to mental health and life-satisfaction. The authors concluded that the improved health benefits in the sport club group compared to individual based PA may result from enhanced social connectedness, social support, peer bonding and self-esteem which may be provided by club support .
Similarly, Miller et al. investigated group (defined as team in the literature) compared to individual sport participation in terms of depression and suicidal behaviour . Team sport was defined as requiring two or more people on the same side to coordinate their movements. Miller et al. found that both participation in team sport and athlete identify were associated with lower depression scores. Specifically, athletic identify mediated the relationship between sport participation and depression.
Recreational and competitive sport
Within club and/or team sport participation there can be different contexts of play, including competitive and recreation participation. One study investigated the contributions of recreational sport and competitive sport to life aspirations and psychological well-being . The prospective design meant that demographic characteristics and participation in recreational versus competitive sport were collected at baseline, and after two weeks, and general psychological well-being was assessed. The life aspirations had a mediating effect on the relationship between participation in recreational and competitive sport and psychological well-being. Furthermore, recreational participants showed a preference for intrinsic life aspirations compared with competitive participants and reported higher psychological well-being . The researchers concluded that the relative importance of intrinsic over extrinsic aspirations is a key dimension in predicting psychological well-being. They proposed that their findings are in line with the Self-Determination theory  given intrinsic motivation is related to personal growth, community contributions, health and meaningful relationships and is far more rewarding and enhances eudemonia and enjoyment compared with extrinsic life aspirations. Furthermore, Chatzisarantis and Hagger argued that, because the focus of recreational participation is not so much on winning compared to competitive sport structures, participants in recreational sport place greater emphasis on intrinsic versus extrinsic life aspirations.
Only one study investigated a single sport being Rugby League . These researchers investigated Rugby League participation across a season and changes in social stress, and how this related to fatigue and injury. There were significant differences observed in social stress between weeks 1 and 4. On the recovery scales significant differences were observed for social recovery between weeks 1 and 5 and general well-being between weeks 2 and 3 .
Other sport participation
Warner and Dixon (2011) interviewed former college athletes and asked them about mechanisms for creating a sense of community within a sport setting. The study found that sense of community was mainly fostered by administrative consideration, leadership opportunities, equity in administrative decisions, competition and social spaces .
Two studies had a less defined measure of sport, with favourite sport  and frequency of participation  being used. In the more recent study, sport participation was defined as how often individuals participated in their favourite sport per week . The authors presented results of frequency of participation to demographics but not to the health outcomes of stress appraisal and emotional distress. However, they did provide detailed information on the types of sports and the associated health outcomes. Sport type-related differences relative to stress appraisal and emotional distress were scarce. However, sport versus no sport participation was associated with significantly less stress and distress. Therefore the differences in the PA to mental health relationship are insignificant as long as the individual’s participation is in the personally favoured types of sport. The authors concluded that, in trying to explain the PA - mental health relationship, previous research has narrowed the spectrum of PA domains down to sport participation. As a result Asztalsos et al. proposed that ‘no one activity fits all recommendations’ in relation to stress appraisal and emotional distress. However they did emphasise the fact that there is an association between specific types of sports and individual preferences, and that it is important for people to choose a sport that suits them best . In particular, individuals who prefer to participate in sport in solitary modes can experience mental health benefits from this chosen form of participation. Specifically, they concluded that such modes of participation can enhance the development of true-self-awareness and personal growth, which is important to social health .
Lastly, Lechner conducted a micro econometric study analysing the effects of sport participation on long-term labour market variables, as well as health and subjective well-being indicators . In addition to the sizeable positive long-term labour market effects in terms of earnings and wages, there were positive effects on health and subjective well-being. The researchers measured sport participation in terms of frequency ranging from at least every week to none. The health measures included the degree of disability, perceived health status and general satisfaction with their health status. Sport was positively associated with all health outcomes.
A conceptual model of Health through Sport is proposed (Figure 2) that is based on three primary categories of outcome as per : physical, psychological and social; and two secondary categories: physical/psychological – aspects involving both the physical and psychological elements, and psychosocial – aspects involving both psychological and social elements.
While our model incorporates all five categories and thus depicts the full range of health aspects, the ‘physical’ aspects have been well reviewed elsewhere  and so this paper in focused on the psychological and social aspects, as defined above.
As previously described , the model includes three major elements: (a) determinants of sports participation, (b) sport itself, and (c) health outcomes of sport participation. The ‘determinants’ element is based on the well-established social ecological model [33, 34] and is represented as concentric rings spreading out from the individual’s intrapersonal characteristics to widening spheres of influence. The sport element incorporates two dimensions of context: individual – team and informal – organised, each of which is almost dichotomous, but also has some intermediate variants (e.g. running alone, running in an informal group, running for a club team, running in a club relay team). The three types of health outcomes - physical, psychological and social - are shown as overlapping, representing the fact that there may be interactions and interrelationships between physical and psychological aspects and between psychological and social health aspects. For example, there are relationships between physical fitness and mental state; and interpersonal relationships may satisfy needs for belongingness and, as such, influence psychological health. Another example is resilience, whereby psychological health may influence an individual’s capacity to engage in interpersonal relationships.
The different strengths of the various linkages between the sport element and the health outcomes represent the notion that all forms of sport contribute strongly to physical health. However, while organised and/or team forms also contribute strongly to psychological and social outcomes, informal and/or individual forms contribute somewhat less to psychological outcomes and relatively little to social outcomes. Finally, we have noted the limited evidence of causality in the literature reviewed. This ambiguity or reciprocity could perhaps be represented by double-headed arrows linking the physical, psychological and social elements to the sport element, but we have represented it by ‘feedback loops’ from the three outputs to the intrapersonal and interpersonal determinants.
The structure of the model proposed is sufficiently general to be applicable both in the adult context and in the context of children and adolescents . Each element and each link shown in Figure 2 is applicable in both contexts. However, the specific details of each element or link may differ between the adult and child/adolescent contexts. The relative importance of specific determinants of participation (within the five social-ecological domains) is not the same for children/adolescents and adults; for example, schools are important organisational settings for sport participation among children and adolescents, but not for adults. The mechanisms of the links between sport participation and psychological and social health also differ at different stages of life; for example, developmental issues are important aspects of the psychological and social health domains for children and adolescents, but not for adults. Also, the feedback loops whereby health status affects intrapersonal and interpersonal determinants of participation are different in detail at different life stages. The main differences between the health outcomes of the children and adolescent compared to adults were that the children and adolescent studies highlighted mainly social health aspects and the adults more psychological. Improved social interaction/integration and social skills and improved self-esteem were the most common health aspects reported in the systematic review for children and adolescents . Whereas the most common health aspects reported in this study related to psychological health aspects of well-being, and reduced stress and distress.
This systematic review has some limitations. Whilst the search strategy, based on a-priori inclusion and exclusion criteria, was comprehensive and encompassed grey literature which reported primary data, conference proceedings were not included. Nor were non-English language articles included. The studies reviewed included a wide range of aims, focuses, measurement tools and indicators of both sport participation and health outcomes. This diversity of focus and methodology limited the extent of synthesis and precluded meta-analysis. Most studies were cross-sectional and used self-report measures. Therefore results should be interpreted with caution, and any conclusions regarding causation are conjectural.