The results from the present study show that the level of mental distress is higher among 18-24-year-old women, compared to both men in the same age group, and older age groups up to 38 years old of both genders. This confirms findings from earlier studies [2–4, 49]. Still, possibly the most interesting finding of this study was the apparent stronger association social support had with young women’s mental health compared to that of young men.
Prevalence of mental distress and gender
A reason why mental distress has a higher prevalence among young women compared to young men, could be because young men have more difficulties in acknowledging their mental health problems and tend to mask this by acting out their difficulties instead . This may result in more externalising disorders, such as antisocial personality disorders and substance abuse or dependence among young men [50, 51]. Young women, on the other hand, report more internalizing disorders such as depression  and anxiety [51–53].
Despite the apparent greater prevalence of mental distress among women and accompanying underlying mechanisms, studies show that externalizing behaviour, more common in men, may be more damaging in the long run, possibly affecting the ability to get a job and build a family later in life [51, 52]. Thus, although levels of mental distress during adolescence and young adulthood are higher among women than among men, the long-term effects in today’s society may be more severe for men.
Gender difference may also be related to the socially defined roles of women and men, which in many societies exposes them to gender-specific stressors . Young women suffer for example more from stressors which involve interpersonal social relationships , experience more restricted gender roles and body dissatisfaction [55, 56], experience more family violence, abuse and school pressure [57, 58], which all have been associated with a greater likelihood of mental health problems .
In understanding the gender difference in prevalence of mental distress another perspective can be found in the field concerned with psychobiology, studying the body’s physiological stress mechanisms . For example. it has been suggested that physiological stress activation occurs partly due to different kind of stressors in men and women . In addition, another consideration in understanding the gender difference in prevalence of mental distress, is the age pattern. In this study, it appears that the prevalence for mental distress reaches its highest level approximately 8–10 years earlier in women than in men. Although not using the same age groups as in this study, Van Droogenbroeck et al. also found different age patterns for psychological distress among girls and boys . It could be questioned whether such patterns could be due to biological differences in maturity, and hence should be taken into consideration, when comparing men and women of the same chronological age. This is a complex field, which encompasses looking at differences in brain development for men and women  and age undergoing puberty related to cognitive development , .
Social support and gender
The study revealed that social support had a stronger association with young women’s mental health compared to that of young men’s mental health. Social support was directly associated with mental health among both young men (18–24 years old) and young women before controlling for the other protective factors. The results of the multivariate analyses however, showed that social support was still associated with mental health problems among young women after controlling for other protective variables. Among young men however, social support was no longer significantly associated with mental health. This suggests that social support may play a key role in the observed difference in mental distress between young women and young men. Our results concerning social support are partly consistent with earlier studies. Earlier studies have showed mixed results regarding whether social support influence differently on mental distress for young males and females. The results from a large review study, showed that social support was a significant protective variable for depression among both young males and females . Another study by Luo et al. from 2017  showed that different social relationships had different impact on mental health among males and females. For girls, same-sex friendships had the strongest social support effect on depressive symptoms, whereas for boys, teacher–student relationships did. Results from a longitudinal Australian study that investigated young people’s mental health over a period of 13 years, showed that the mental health of females appeared to benefit slightly more from higher levels of social support from friends and family than males .
A possible reason why social support seem to be a more important protective factor for mental distress among young females compare to males may be found in previous studies that have shown that young females experience more stress in interpersonal social relationships and are more likely to become depressed as a consequence of peer and family stress exposure compared to young males, [54, 63–65].
A gender difference in statistical significance was also present in the oldest group, 32–38 years old. However, in this group there was almost the same odds ratio for both men and women, and the confidence intervals strongly overlapped.
Regular physical activity alone was significantly associated with mental health problems among young women (18–24 years). Physical activity was however not a significant predictor among young women when controlled for other protective factors such as social support, SOC, and participation in organized and unorganized activities. Thus, it seems like social support and SOC was the most important protective factors for mental health among young women, and that the social aspects of physical activity and the way activities gave meaning in daily life, were more important for young women’s mental health. Previous studies are partly consistent with these findings [66–69]. In addition, previous research has showed that participating in social activities, like team sports, is more important for mental health than physical activity per se [70–74].
Sense of coherence
The results from the present study show that SOC was highly associated with mental health in both males and females in all included age groups. This likely emphasises how the perception that everyday life events are comprehensible, meaningful and possible to master (manageability), have a positive impact on mental health, regardless of gender among those 18 to 38 years old. This is consistent with the studies of Antonovsky , who argued that SOC is a cross-cultural concept and that it is human to seek understanding, to cope with daily challenges, and to seek meaning of the various aspects of life.
Super et al.  suggested two closely interlinked processes, based on an exploration of the salutogenic model, that may need to be included in health promotion activities with the aim to strengthen SOC. In short these two are the process of empowering people to identify appropriate resources to deal with everyday stressors and the second process is focused on facilitating reflection to increase understanding of the stressor they are facing, to better identify available resources and to give a feeling that dealing with stressors can be meaningful. In this article the authors refer to a selection of intervention studies that has been successful in increasing SOC levels. They argue that for example the study by  contained group interventions that targeted both empowerment and reflection in employees with severe burnout symptoms.
Limitations of the study
It is important to stress that these analyses are based on cross-sectional survey data. Thus, it is neither possible to decide whether there really is causation, nor is it possible to point out the direction of the suggested causation. Young women may experience mental problems because of a lack of social support. On the other hand, it is also possible that mental problems influence social support, e.g. that young women with mental problems withdraw from other people or are excluded from social groups. Although the data are not suitable for examining causation, a cross-sectional study may reveal significant gender differences when predictors for mental problems are concerned.
As implicated by Kocalevent et al., the Oslo-3 scale might be used in different ways . Scoring two questions from 1 to 5 and one question from 1 to 4, yields a total score between 3 and 14. Also one may use a dichotomous version of this instrument, and usually 9.0 as a cut-off has been recommended. In general, and as far as possible, the choice of cut-off should be based on the statistical properties of the variable under consideration. In the present material, there were very few young men scoring below 9.0. In order to meet this challenge, a higher cut-off level of 10.0 was used for both genders.
Another limitation of the study is the low response rate of 23% among the youngest age group (18–24 years), particularly among young men. This may have led to selection bias.
The subsample used for this study was not checked for selection bias, but the complete material from the cross-sectional health survey showed an increasing response for older age up to 80 years old, and noticeably, but less than for age, a higher proportion of women and of those with completed higher education participating. A certain amount of selection bias may therefore be assumed, but it is difficult to determine how this may have impacted the findings of this study.
Another limitation of this study was the number of protective factors available for analysis. The questionnaire was primarily designed with the aim of giving sufficient overview of the population health of the participating counties, and at the same time ensuring a short questionnaire.
Sociodemographic covariates, like education, income and employment are important in the general adult population, but not necessarily correct or representative of socioeconomic status for young adults. The majority of young Norwegians under 25 have neither finished their education, nor have they acquired high-paying jobs yet. Many of our study participants are therefore too young to offer good data on education, employment and income, and these variables were not included in the study. Family background, like parents’ education and income, may be more relevant and important background factors, but such data were not available.
Implications of the study
Bearing in mind that the material for this study originated from a general public health survey, without defining a specific setting or target group other than age, the findings may still be interesting and relevant to research in different fields and for various groups of young adults and practical settings. From a public administration and public policy making perspective there is a desire to both gain a greater understanding of and simultaneously achieve a reduction in the apparent high prevalence of mental distress in the general population, particularly among young women. With this perspective in mind, two areas of focus are suggested. Firstly, a further exploration of whether there are specific aspects of social support that especially need attention among young adults. For example, Jiang et al.  found an age difference in type of social support seeking comparing older adults (age 60+) and young adults (age 18–25). Compared to older adults, young adults were found to seek more explicit social support, that is, emotional comfort that involves disclosure and discussion of problems and the request for assistance. After such an identification the next step would be to gain understanding of opportunities on how to strengthen those specific aspects of social support.
Secondly, the findings add support to existing, and hopefully will inspire to new, health promotion activities that have a focus on increasing SOC, including activities that strengthens social support as an available resistance resource. In the literature there appear to be more examples of mental health promoting interventions including specific at risk or treatment groups [77, 78], but the principles of empowerment and findings on influence on social capital and social cohesion are relevant. Health promoting activities with such a salutogenic perspective may benefit from careful attention to including elements of both empowerment and reflection . In addition, attention to strengthening both individual and group level SOC may be relevant . Interventions may also include attention to how the environmental conditions for health may be changed, and then specifically regarding changes that may increase mental health through access to social support. This for example by increasing opportunities for social interactions in the physical environment or through organized activities. Commers et al.  proposed an analytical instrument to use for strategies to influence various aspects of physical and social environments for health. Included in this instrument is the role of the public health professional when empowering groups or individuals to gain ability to undertake suitable environmental actions.
Finally, it may be important to emphasize that most of young adult women 18–24 years old, are in an educational setting, and as such this is possibly where suitable changes or interventions for increased social support may be most relevant, although local communities may also play a role.