Physical activity (PA) seems related to mental health and wellbeing. Since some decades, exercise has been suggested to be associated with better mental health [1
]. Similarly, wellness has been described as a concept that underlines the importance of PA for the feeling of wellbeing [3
Unsurprisingly, in recent years, studies have explored the role of PA as a potential component in the prevention and/or management of depressive symptoms [4
]. Reviews of observational and intervention studies examined the links between PA and depression/depressive symptoms [5
]. Several appraisals indicated parallel conclusions: that PA was positively associated with reduced likelihood of depression or depressive symptoms [8
]. Indeed, observational [9
] and intervention research [12
] found that higher levels of PA (e.g., >60 minutes of PA per week) were associated with lower odds of depression. Moreover, others [14
] concluded that even low levels of PA (e.g., exercising as little as 30 minutes per week) were associated with enhanced mental health.
Nevertheless, cross-sectional [17
] and prospective inquiries [20
] suggested conflicting inconsistencies on the association between PA and depression. On the one hand, three community-based longitudinal inquiries concluded that PA was not protective for subsequent depression [23
]. However the samples examined in these studies were not homogenous: Cooper-Patrick et al.
] and Lennox et al.
] examined only middle-aged men, whilst Weyerer [25
] included males and females as well as older subjects. On the other hand, another three community-based inquiries [20
] found a protective effect of PA on depression. Again, the samples were not homogenous: Paffenbarger et al.
] limited their inquiry to male college students; Camacho et al.
] and Farmer et al.
] included men and women of a very wide age range, and whilst the former reported a protective effect of PA on depression for both men and women, the latter found an effect only for females.
The inconsistent findings of these studies draw attention to the need for a range of confounding features related to depression (e.g., unhealthy lifestyle), along with other aspects to be taken into account when assessing the links between physical exercise and well-being [10
]. Thus, in gauging the association between PA and depressive symptoms, several demographic, behavioural, social, and academic factors need to be simultaneously considered [28
] has suggested that moderate to high levels of weekly energy expenditure in men were associated with decreased likelihood of depression. Conversely, others [20
] reported a protective effect of PA on depression only for women. Thus, the current study included male and female university students as participants.
Self-rated health status (perceived health)
: in the U.S.A., high-school students’ self-reported health status was modestly correlated (r
0.09 to 0.22) with five life domains (satisfaction with family, friends, school, living environment, and self) and overall life satisfaction (r = 0.21) [29
]. In relation to one another, depressive symptoms were more strongly associated with self-reported mental health status, while PA was more strongly linked with self-reported physical health [30
]. Perceived health incorporates physical, emotional and personal components of health that collectively make up individual “healthiness” ([14
], p. 242). As such, perceived health seems a broader indicator of health-related wellbeing. Some authors [10
] have proposed a relationship between PA and decreasing depressive symptoms in middle-aged women, independent of pre-existing physical and psychological health. Hence we included self-rated health status in the current investigation of the links between PA and depressive symptoms.
: from the mental health perspective, teens in primary care settings were not seeking mental health care even when depression was detected, suggesting that such adolescents may be at different stages of recognition of their conditions [31
], or might benefit from more awareness. Likewise, many persons with schizophrenia were unaware of the symptoms and consequences of their condition, and such unawareness was a risk factor for poor adherence to treatment and poor outcomes [32
]. From the PA perspective, there is a need for a greater understanding of the (perhaps yet anticipated) antecedents of PA participation [33
]. In such context, enhanced health awareness/consciousness could play a role as determinants of an active lifestyle and in negotiating a physical identity, and could be drivers for a commitment towards PA. Indeed, a proposed explanation for the limited effectiveness of PA interventions is that people may lack awareness of their health behaviour [34
]. As health awareness appeared to be related to mental health and PA, we included it in the current investigation of the PA-depressive symptoms relationships.
: education or academic achievement seem interrelated with both PA and mental health. In relation to PA, a link between physical fitness and academic achievement in elementary school children has been suggested [35
]. In Swedish 9th-grade pupils, academic achievement was associated with vigorous PA in girls [36
]. In the USA, promoting fitness of school pupils by increasing their PA opportunities enhanced the pupils’ academic achievement even after controlling for potentially confounding factors [37
As regards mental health, exercise could be a simple yet significant way of enhancing those aspects of children’s mental functioning central to cognitive development [38
]. The well educated tend to be mentally and physically healthier than the less well educated [39
], and, poor academic achievement is a risk for later depression [41
]. The association between depressive symptoms during adolescence and educational attainment in young adulthood [42
] indicate that depressive symptoms were associated with higher odds of failure to complete high school (only for girls). Among high school graduates (both genders), depressive symptomatology was associated with failure to enter college.
Furthermore, in connection with body image, cognitive development in adolescents could be linked to weight perception and body image [43
]; and tools that measure depressive symptoms (e.g., Modified Beck Depression Inventory, MBDI) include questions about one’s appearance [44
]. Despite this, surprisingly, El Ansari and Stock [47
] recently examined a sample of UK university students and found that neither PA nor depressive symptoms were significantly associated with three different subjective and objective measures of academic achievement. Notwithstanding, there have been calls to examine the relationship between mental health problems and factors such as educational attainment, that impact physical health later in life [42
]. We included educational achievement in assessing the relationships between PA and depressive symptoms.
Strengthening or toning exercises
: PA appears to be inversely related to the risk of depression [8
]. However, although leisure-time PA is inversely associated with depression among females [48
], few have explored the association with PA undertaken in other domains (e.g., work-, domestic- and transport-related) [50
]. Others failed to control for involvement in non-aerobic activity [51
], or other forms of PA e.g., strengthening or toning exercises. This is despite that among healthy older adults, resistance training has been associated with improved mood states [54
]; and moderate- or high-intensity muscle-strengthening activities two or more days a week provided additional health benefits [55
]. Interpretive difficulties arise due to such lack of control for the potential factors that could influence the PA-depression relationship. This suggested that it was important to include strengthening or toning exercises in the current study of the links between PA and depressive symptoms.
Intensity of physical activity
(dose-response relationships between PA and depressive symptoms
): Several studies reported lower depressive symptomatology among physically active males and females [56
]. In support, longitudinal, cross-sectional and intervention research [15
] found significant inverse associations between moderate-intensity PA and odds of depression. Fewer studies examined the relative strengths of associations between moderate or high intensity PA and the risk of depression [59
]. A follow up of 21,596 men for 20 years showed a dose-response relationship between PA and physician-diagnosed depression [26
]. Recently, links between increasing PA and declining depressive symptoms in middle-aged females, independent of pre-existing physical/psychological health have been suggested [10
]. Hence in the present study, we included several forms (levels) of PA: low; moderate
; and vigorous
: the role of PA in a health-seeking life style seems increasingly about the improvement of one’s silhouette, where for instance, many women exercise in order to achieve a better silhouette [61
]. Most cultures assign importance to appearance [62
]. In Western traditions, being slim and fit signifies a high marketing value of self-control and personal success [63
]. Moreover, obesity appears associated with depression, low self-esteem, and poorer quality of life [64
]. Negative social and emotional associations of overweight and obesity e.g., low self-esteem, depression, behavioural and learning problems have also been suggested [66
]. There is some evidence of greater risk of depression among the obese [69
In line with others [5
], for this paper, we use the terms ‘depression/depressive symptoms/depressive symptomatology’ variously to describe a dysphoric mood state, a syndrome of a cluster of symptoms (e.g., sadness, fatigue, loss of appetite, disturbed sleep, disappointment with oneself and other self-reported experiences). PA was defined as “any bodily movement produced by skeletal muscles that result in energy expenditure” ([72
Aim of the Study: Based on the above background, the main aim of the current study was to assess the association between depression and PA in university students of both genders. We assumed that PA is inversely associated with depression even when controlled for other factors. In order to control for a range of factors that have previously been shown to be associated with PA as well as with depression (gender; perceived health; educational achievement; strengthening or toning exercises; and body image perception), these variables were included into the analysis in order to control for potential confounders.
We examined three different levels of PA (low, moderate and vigorous) as dependent variables in order to analyse any dose-response differences in the association based on level of PA. We hypothesized that university students who achieved recommended guidelines of vigorous PA would exhibit lower levels of depressive symptomatology than students who achieved recommended levels of moderate PA. The highest level of depression would be expected in students not engaged in any level of PA.
A second sub aim of the analysis was to study the role of body image perception as a potential effect modifier of the relationship between PA and depressive symptomatology. We hypothesized that the inverse association between depression and PA might be stronger in students who perceived their body image as ‘just right’ when compared to students who perceived their body image as ‘overweight’.