Introduction
Mental disorders are among the leading causes of disability and disease worldwide and estimates suggest a higher burden of mortality among individuals and populations with mental disorders [
1,
2]. Across the European Union, mental illnesses have been reported to affect more than one in six adults, and the social and economic costs are substantial [
3]. The strong positive relationship between mental distress and mental disorder and the strong negative relationship between mental distress and mental wellbeing [
4], underlines the importance of identifying modifiable factors that may prevent development of mental distress and mental illness in the general population.
Healthy lifestyle behaviors, such as higher levels of physical activity, have been associated with reduced risk of mental distress [
5]. Moreover, evidence reported by research literature reviews suggest a dose-response relationship and that any level of physical activity seem to decrease the risk of developing depressive symptoms [
6,
7]. Observations among a representative sample of Canadian adults have confirmed a dose-response relationship between objectively measured physical activity and improved mental health but also suggested that physical activity and mental health associations could be hampered by daily sedentary time [
8]. A positive association between sedentary time and mental distress, independent of physical activity level was also confirmed by a cross-sectional study among Belgian adults [
9]. In addition, studies have identified short sleep duration as a risk factor for depression [
10,
11] and mental distress [
12], and that sleep distrubances are independently and strongly associated with poor health-related quality of life in middle-aged and older adults [
13].
Involvement in organized activities, such as cultural engagement and participation in sport, has also been suggested to be an independent risk-reducing factor for development of depressive symptoms [
14,
15]. Further, as involvement in social organized activities seemed to predict both higher quality of life and lower levels of depressive symptoms [
16], development and maintenance of organized sport and recreational activities that are socially and culturally relevant has been supported [
17].
Several studies, especially among elderly, have also confirmed that social support plays an independent and important role in enhancing and maintaining improved mental wellbeing [
18‐
21]. Further, results indicating a significant association between social support from friends, spouse or relatives and reduced odds of panic disorder and mental distress, especially when the severity of mental health problems are low, highlights the importance of social networks and support [
22]. On the other hand, a cross-sectional register study among Danish adults showed that individuals with less frequent social encounters than desired and those with less contact with family and friends than once a month had increased risk for poor mental health [
23].
Most previous studies investigating associations between modifiable lifestyle behaviors, participation in organized activities, social support and mental distress are hampered by low participation rate, low quality of the studies and focus on few explanatory factors of mental distress [
5,
24,
25]. Thus, the present study contributes to the existing literature by examining possible associations between a range of modifiable factors, including low level of leisure-time physical activity, high sedentary time, low participation in organized activities, low social support, sleep problems and mental distress among a large sample of Norwegian adults.
Results
The sample comprised 13.122 men (46.8%) and 14.925 women (53.2%) in which a total of 1538 men (12%) and 2256 women (15%) reported mental distress, respectively. Compared to women, a higher number of men reported high sedentary time, low participation in organized activities and low social support, whereas a higher number of women than men reported to have sleep problems (p < 0.001 for all). No gender differences in leisure-time physical activity were identified.
Among individuals with low leisure-time physical activity and high sedentary time, a higher proportion of women than men reported mental distress (16% vs. 13 and 19% vs. 15%, respectively). Likewise, among individuals with low participation in organized activities and low social support, a higher proportion of women than men reported mental distress (24% vs. 17 and 23% vs. 17%, respectively). Our results revealed no gender difference in the association between sleep problems and mental distress.
For men, binary logistic regression analyses adjusted for perceived financial situation and age showed that the odds of having mental distress was increased among individuals reporting low leisure-time physical activity (OR: 1.18; 95%CI: 1.03–1.37), high sedentary time (OR: 1.32, 1.16–1.51), low involvement in organized activities (1.43; 1.25–1.64), low social support (2.55; 2.18–2.99), and sleep problems (7.29; 6.35–8.37) compared to the rest of the male population.
For women, adjusted model showed that the odds of having mental distress was increased among those reporting high sedentary time (1.25; 1.11–1.39), low involvement in organized activities (1.60; 1.42–1.80), low social support (2.71; 2.39–3.06), and sleep problems (5.78; 5.15–6.50) compared to the rest of the female population. No significant association was shown between low leisure-time physical activity and mental distress among women after adjustment for age and financial situation.
Discussion
Results from the present cross-sectional study showed an association between lifestyle risk factors and mental distress in a large sample of adults living in Southern Norway.
Our study revealed an association between low leisure-time physical activity and mental distress, but not for woman after controlling for possible confounders. A previous meta-analysis confirmed that physical activity seems to reduce depression by a medium effect and anxiety by a small effect in non-clinical populations [
33] and results from a thirteen-year prospective cohort study indicated that both light and moderate to vigorous leisure-time physical activity may play a protective role against mental distress [
34]. In line with our results, another meta-analysis has reported that gender may modify the effect of physical activity on incident depression [
7], whereas another meta-analysis has suggested that the potential protective association of physical activity on depressive symptoms and depression is similar for men and woman [
35]. The association between depression and physical activity appears to be bidirectional; physical activity may prevent and alleviate depressive symptoms in the general population and, in turn, having depressive symptoms in early adulthood may be perceived as a barrier to physical activity [
36]. Results from previous studies suggest that regular physical activity recruits a process which results in enhanced emotional resilience to stress [
37,
38]. However, possible mechanisms explaining observed effects of physical activity on mental distress are most likely complex and might be manifested at psychological (e.g., by improving mood, feelings of mastery, self-efficacy) and neurophysiological (e.g., by increasing synthesis and release of neurotransmitters and neurotrophic factors associated with neurogenesis, angiogenesis and neuroplasticity) levels [
39,
40].
Further, our results confirmed an association between high sedentary time (≥8 h/day) and mental distress in both men and women. Systematics reviews have suggested a small positive association between sedentary time and symptoms of both anxiety and depression, but also highlighted that only a few studies, with partly inconsistent results, had examined this relationship [
41,
42]. In addition, previous cross-sectional studies have confirmed an association between high sedentary time and mental distress [
29,
43]. A possible explanation for the observed relationship between sedentary time and mental distress is that high sedentary time may displace physical activity, which has been shown to reduce levels of mental health problems [
44]. High sedentary time may also be an independent risk factor of mental distress as uninterrupted sedentary time seems to moderate and deleterious insulin sensitivity changes, glucose tolerance, and plasma triglyceride levels, which indirectly could affect mood and well-being [
45].
Research has indicated that participation in organized activities provide a sense of belonging, value, and attachment [
24], and may thereby have a positive influence on mental health. Whereas our study used a broad approach to identify participation in organized activities by including focus on both involvement in physical activity groups, political teams, volunteer work, religious communities, as well as clubs, most previous studies have focused solely on whether participation in physical activity groups may be associated with improved mental health. Results from the present study indicated that low involvement in organized activities was associated with increased odds of mental distress, both among men and women. These findings are supported by results from prospective studies among European adults suggesting that involvement in social organized activities predicted higher quality of life and lower level of depressive symptoms over time and be a protective factor against the onset or development of chronic conditions, especially among individuals with few close social ties [
16,
46]. Finally, a Norwegian population-based study has suggested a dose-response effect of participation in organized activities on perceived health, anxiety, depression, and satisfaction with life in both women and men, and that men who engaged specifically in receptive, rather than creative, cultural activities reported better health-related outcomes [
47]. However, few longitudinal and experimental studies have examined gender dependent effects of participation in different organized activities on mental health.
Similar to our results, several other studies have also reported that lower level of perceived social support are associated with mental distress in both men and women [
48,
49]. Furthermore, among older individuals who lacked social support, women seemed to need more emotional support whereas men seemed to need more tangible support [
48]. A longitudinal study among British adults has also confirmed a bidirectional relationship between social support and mental health and that the relationship varied over the life course [
50]. Furthermore, low social integration among peers in adolescence has recently been shown to predict higher levels of depression among US adults [
51], and systematic reviews have reported evidence linking low of social support, social isolation, and loneliness to mental health problems [
25,
52]. On the other hand, having trust in people, feeling safe in the community, and having social reciprocity has been identified as factors associated with lower risk of mental distress [
53]. Previous studies have argued that high perceived social support could play a key role in reducing risk factors of mental distress caused by negative life events, such as job loss and marriage break-down [
54,
55].
Finally, the current study showed that having sleep problems was strongly associated with increased odds of mental distress in both men and women. Results from previous studies indicated a U-shaped association between sleep duration and mental distress [
56], and that individuals who experienced both insomnia and short (< 7 h) sleep duration had increased risk of chronic mental health symptoms [
57]. Moreover, a study among Norwegian adults confirmed that different symptoms of insomnia seemed to play a key role in rising of anxiety levels [
58] and a meta-analysis indicated that non-depressed subjects with insomnia had a twofold risk of developing depression compared to those with no sleep difficulties [
59]. Studies have also suggested a bidirectional relationship between sleep problems and mental distress, and that mental distress increase the risk of experiencing insomnia later in life [
60,
61]. Underlying psychophysiological mechanisms through which insomnia, or general sleep problems, predicts mental distress are still not clear. Previous studies, however, have raised attention to the role of sleep in emotion regulation [
62], and from a neurobiological perspective, a dysfunction in sleep-wake regulating neural circuits may lead to alterations in emotional reactivity [
63].
Several methodological limitations of the present study should be considered. This study’s main limitation is the cross-sectional design which precludes inferences about causality. Further, the present study relied on self-reported measures which are prone to memory and recall bias, as well as social-desirability bias. Despite a limited participation rate and a higher proportion of high educated participants compared to the total adult population in Norway (48% versus 34%) [
64], a major strength of the present study was the large sample drawn randomly from a general population. Another strength is that we used validated tools to measure mental distress (HSCL-5) and social support (OSS-3) [
65‐
67], and that data reflecting frequency, duration and intensity and duration of leisure-time physical activity were combined to identify individuals who achieved the WHO recommendations [
30]. Further, perceived financial difficulties, has previously been identified as a major contributor to mental distress [
68] and was therefore used as a measure of socioeconomic status in the present study.
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