Research has shown that young adults consume high amounts of fast food and soda or sugar-sweetened beverages and low amounts of fruits and vegetables [1,2,3,4,5,6]. For the purpose of this study, we define soda or sugar-sweetened beverages and fast food as unhealthy foods, and fruits and vegetables as healthy foods. Moreover, compared to other age groups, young adults are more likely to exhibit symptoms of depression, and young women are more likely to report depression than young men [7,8,9,10,11,12,13,14]. Further, researchers have found that fast food and soda consumption are positively associated with depression among young women, while fruit and vegetable consumption are negatively associated with depression [15,16,17,18]. Scientists have found that nutrition and food consumption affects mood and depression through a variety of nutritional deficiencies, which thereby affect neurotransmitters in the brain that are associated with depression, including serotonin, dopamine, and noradrenaline . Therefore, the relationship between food consumption and depression is of interest for physical and social scientists alike.
In this study, we also examine unemployment, which is highest in young adulthood [20,21,22]. Researchers have also found that unemployment in young adulthood is positively associated with depression [23,24,25], as well as an increased consumption of fast food and soda and decreased consumption of fruits and vegetables . Therefore, studies have shown that food consumption is associated with unemployment and depression, and also that unemployment is associated with depression. However, little is known about the moderating role of unemployment on the relationship between food consumption and depression. In this study, we address this gap in the literature by examining the relationship between food consumption and depression with unemployment as a moderator, particularly among young women. To explore these relationships, we utilized cross-sectional data from one wave of the National Longitudinal Survey of Youth 79 for Children and Young Adults (NLSY79 CY) collected in 2014.
Young women’s food consumption
Researchers have found differences in the food consumption of young men and women [5, 27,28,29,30,31,32,33]. From adolescence to older adulthood, males are more likely than females to drink soda and consume fast food [5, 28,29,30,31,32,33]. There is also a gender difference in the pattern of fast food consumption, with men more likely than women to consume fast food for lunch (48.3% vs. 39.1%), while women are more likely to consume fast food as a snack (25.7% vs. 19.5%) . However, females are more likely than males to consume fruits and vegetables [34, 35].
Despite these gender differences across multiple age groups in healthy and unhealthy food consumption, it is of interest to examine young women’s food consumption. Researchers have found that women are more likely to consume soda or other sugar-sweetened beverages and fast food and less likely to consume fruits and vegetables during young adulthood than in later periods of adulthood [1,2,3,4,5,6, 32, 33, 36, 37]. Compared to adolescents and children, young adults’ consumption of healthy and unhealthy foods are relatively similar , with some evidence suggesting that children and adolescents consume slightly more fast food and soda than young adults [2, 39].
Prevalence of depression among young women
The prevalence of major depression in young adulthood is high, and it is most likely to emerge during this developmental period [8, 10, 11]. Results from the 2017 National Survey of Drug Use and Health reveal that the prevalence of major depression was highest during young adulthood (ages 18 to 25), at 13.1% . Results from the National Epidemiologic Survey on Alcohol and Related Conditions-III similarly revealed that young adults were more likely to be diagnosed with major depression than older adults . Moreover, researchers have found that the prevalence of major depression in young adulthood is increasing over time [40, 41]. From 2005 to 2014, young adults’ prevalence of major depression increased from 8.8 to 9.6% . Additionally, from 1998 to 2017, the percentage of young adults reporting at least two symptoms of major depression in the past 30 days increased among those aged 18 to 24 years (4.4–7.3%), as well as among those aged 25 to 29 years (4.6–5.5%) .
Researchers also consistently have found that females are more likely to experience major depression than males across most ages [7,8,9, 12, 42]. These findings were consistent across cultures and in a meta-analysis of 90 studies [7, 9]. Researchers have found that before puberty, girls and boys are equally likely to exhibit symptoms of depression, but this prevalence peaks at ages 14 to 25 and decreases with age, although women remain more likely to report depression than men . In one sample of college athletes, female athletes were 1.84 times more likely to experience major depression than their male counterparts . Additionally, researchers found that female college students are more likely than male college students to experience depression overall and to report symptoms of physiological agitation related to depression .
Food consumption and depression
Unhealthy food consumption and depression
Four studies examined the relationship between fast food or soda consumption and depression in young adulthood [15, 16, 18, 44]. Findings on the relationship between fast food consumption and depression have been mixed, suggesting more research is needed in this area. One of these studies found a positive association between fast food consumption and depression in male and female college students in the United Kingdom . In another, fast food consumption was positively associated with depression only among Mexican female college students, but not their male counterparts . In the third, there was no significant relationship found between fast food consumption and depression in a sample of Lebanese college students . Moreover, findings on the relationship between soda consumption and depression in young adulthood are similarly mixed [15, 18]. In a sample of Chinese college students, those students who drank soda more than seven times weekly were more depressed than students who infrequently drank soda . However, in another sample of college students in the United Kingdom, soda consumption was not significantly associated with depression . Additionally, although not focused on young adulthood specifically, results from a meta-analysis revealed a positive association between depression and soda consumption that did not vary by gender, country, alcohol consumption, smoking or level of physical activity . Further, researchers examined gender differences in the relationship between sugar-sweetened beverage consumption and depression, and in two studies the relationship was stronger among women than men [46, 47].
Healthy food consumption and depression
Two studies examined the relationship between vegetable and fruit consumption and depression in young adulthood. These studies both revealed that the consumption of more fruits and vegetables was associated with lower levels of depression among college students in multiple countries [15, 17]. Further, these relationships may differ by gender; researchers found significant associations between increased vegetable consumption and fruit consumption and lower depression among adult women but not among adult men .
The role of employment on the relationship between young women’s food consumption and depression
Although young adult employment rates in the United States have been steadily decreasing from a high of 18.29% in 2010, unemployment rates in October 2018 were still highest among those aged 16 to 24 (8.3%) and lowest among those aged 45 to 54 (2.7%) [21, 22]. Further, researchers have found that unemployment during young adulthood is positively associated with depression [23,24,25]. Using results from the 1979–1994 National Longitudinal Survey of Youth, researchers found that being currently unemployed or out of the labor force was positively associated with depression among adults 29–37 . Additionally, using 2010 Behavioral Risk Factor Surveillance System survey data, researchers found that among emerging adults aged 18 to 25, depression was more likely among the unemployed (23.4%) than the employed (8.4%) . Moreover, a systematic review of 20 studies published between 2004 and 2014 showed that job insecurity and unemployment were significantly related with higher depression .
Unemployment and food consumption
Researchers have found that unemployment status is significantly associated with decreased consumption of fruits and vegetables across age groups [26, 49,50,51]. For instance, results from the 1990–2009 U.S. Behavioral Risk Factor Surveillance System survey indicate that at the population level, a 1% increase in the unemployment rate in the state in which one resides is correlated with a 3–6% reduction in the consumption of fruits and vegetables among those at the highest risk of being unemployed . Interestingly, this impact is slightly higher in young adulthood than at other ages . Further, an examination of fruit and vegetable consumption among Icelandic adults during the Icelandic economic crisis showed that fruit and vegetable consumption reduced during the crisis at an estimated 5% for vegetables and 10% for fruits .
Furthermore, five studies examined the relationship between unemployment and fast food or soda consumption, and there have been some mixed findings [26, 49, 52,53,54]. According to data from the National Longitudinal Survey of Youth-1979, being unemployed is associated with fewer fast food purchases . Additionally, researchers who examined the impact of the 2008 Icelandic economic crisis on soda and fast food consumption found that being unemployed was associated with decreased consumption of both; for fast food consumption, this relationship was explained almost entirely by higher mortgage debt the crisis caused . Researchers also examined fast food consumption among overweight and obese pregnant women and they found that women who were unemployed ate more fast food than their employed counterparts .