The Many Faces of Stress: Three Factors that Predict Physical Illness in Young Adults

Abstract

Three studies examined how various forms of stress uniquely contribute to physical illness. We compared negative affect and perceived stress in Study 1, neuroticism and perceived stress in Study 2, and negative affect, neuroticism, and perceived stress in Study 3. We also controlled for health-related covariates (i.e., exercise, nutrition, substance use, and BMI). In all three studies (ns = 271, 577, and 300), participants completed online surveys for course credit. The results of Study 1 demonstrated that both negative affect and perceived stress predicted physical illness. In Study 2, neuroticism and perceived stress each predicted illness symptoms, and an additional interaction between neuroticism and perceived stress, were found. In Study 3, where all three stress factors were included, only negative affect predicted illness symptoms. Taken together, these results suggest that negative affect uniquely explains most of the variance in physical illness symptoms while controlling for other forms of stress.

Keywords

Physical illness illness symptomatology negative affect neuroticism perceived stress stress

Introduction

Stress affects everyone negatively, despite their age, gender, or socioeconomic status (Salleh, 2008). In the United States alone, nearly half of all adults have at least one chronic health condition (Centers for Disease Control and Prevention, 2015), and many of these conditions can be linked to stress. Although some short-term stress has been shown to boost the immune system, chronic stress can lead to chronic illness such as cancer (Coroiu et al., 2016), diabetes (Morris et al., 2011), and cardiovascular disease (Kashani et al., 2012). Stress can be defined as chronic personality traits and situational stressors, but the distinctive contributions of each to the onset of illness symptoms has not been determined. Including multiple assessments of stress is essential to understanding physical illness, but these types of stress are rarely examined independently of one another. The purpose of the present research is to examine multiple stress factors to determine how they uniquely predict of physical illness symptomatology. For our research, we focus on three major types: negative affect, neuroticism, and perceived stress.

Three types of stress

Stress has been defined across a wide variety of contexts and psychological processes. These forms of stress have been examined at both the trait and state level and they are all linked to physical illness, but their definitions are often conflated with each other (see Scherer, 2005 for a review). The following section defines these three types of stress, their interconnectedness, and their associations with physical illness.

Negative affect (NA) is an overall experience of negative emotions like anger, fear, and anxiety (Watson & Pennebaker, 1989) and is also largely heritable (Baker et al., 1992). It can occur as a brief state, a long-lasting experience, or a stable trait (Pressman & Cohen, 2005; Smith et al., 2018). Often, however, negative affect is defined as a stable trait (Elkins et al., 1999), best assessed through the Positive and Negative Affect Scales (PANAS; Watson & Tellegen, 1985). NA is consistently linked to physical illness, but it may depend on additional circumstances such as symptom reporting. For example, individuals with trait negative affect appear to be more sensitive to their symptoms (Cameron et al., 1998). In a recent nine-year longitudinal study, McAndrew et al. (2014) found that those high in trait NA with a chronic illness report more physical symptoms of their illness and believe that their symptoms impact their functioning greater than those who do not score high in NA. Similarly, Brown and Moskowitz’s (1997) event-sampling study found a strong association between instances of feeling negative affect and symptom reporting.

Neuroticism is another form of stress that is linked to symptom reporting. It is a highly heritable trait; between 40%-60% of the variance in the expression of neuroticism is accounted for by genetics (Barlow et al., 2014). Those who are highly neurotic tend to experience higher levels of depression, guilt, envy, and anxiety than others (Weber et al., 2013). Similar to negative affect, neuroticism is linked to poor health outcomes; Costa and McCrae’s (1985) longitudinal study found that individuals who scored high in neuroticism reported two to three times as many symptoms than those who scored low on the trait.

Perceived stress occurs when an individual judges that situational demands exceed her or his resources (Lazarus & Folkman, 1984). This form of stress occurs when one’s environment is deemed threatening, harmful, or a risk to bodily or psychological functions (Cohen et al., 1995; Grant et al., 2003). Similar to negative affect, perceived stress has been defined as a highly heritable trait (Kim et al., 2016; Morgan et al., 2014; Rietschel et al., 2014; Rietschel et al., 2016) as well as a state-level stress outcome (e.g., Şahin & Çetin, 2017). Regardless of its definition, perceived stress also consistently predicts illness susceptibility (Lepore, Miles, & Levy, 1997), with detrimental health and performance outcomes in the workplace (e.g., Bergomi et al., 2017; Landsbergis et al., 2001) and in school (e.g., Hurst et al., 2013).

Since their inception, the definitions of and connections among these three stress factors vary across investigations, depending on whether the constructs are defined as chronic traits or situational states. Regardless of the methodological frame, all three have a strong positive link to each other (Abbasi, 2016). In many cases, neuroticism is defined as a highly heritable and stable personality trait that predicts chronically high levels of perceived stress (Bruck & Allen, 2003; Hills & Norvell, 1991; Fogelman et al., 2016; Gunthert et al., 1999; Hasel et al., 2013; Lu et al., 2014; Rietschel et al., 2014, 2016) and negative affect (Mooradian & Olver, 1994; Newman & Llera, 2011; Rusting & Larsen, 1997). In other instances, neuroticism is used as a trait predictor of state perceived stress (Jiang et al., 2017; Pereira-Morales et al., 2017; Şahin & Çetin, 2017) and state-level negative affect (Abbasi, 2016).

Although these three stress factors are consistently linked with illness symptoms, examinations of these associations have only focused on some of the factors and a narrow set of effects. For example, negative affect is the strongest predictor of medically unexplained symptoms (De Gucht et al., 2004) and symptom reporting (Brown & Moskowitz, 1997) even when accounting for neuroticism and for a negative affect × neuroticism interaction effect, but perceived stress was not accounted for in these studies. Perceived stress has also been identified as a mediator between neuroticism and depression (Pereira-Morales et al., 2017), but negative affect was not included in the investigation. The factors can also interact, creating an additive effect on the experience of illness symptoms (Endler & Kocovski, 2001). This suggests that someone who scores high in trait stress and is also in a particularly stressful environmental state will report more symptoms of illness than someone who has only one or neither of those conditions. Thus, it is important to account for this interaction when examining the role of different forms of stress on physical health.

It is also important to note that stress is not the only factor that can lead to higher rates of physical illness. There are many other health factors that can influence the way people experience physical illness and symptoms of illness. According to the National Heart, Lung, and Blood Institute (2017) there are many risk factors associated with having a high body mass index (BMI), such as high blood sugar, high blood pressure, and high cholesterol. Having a poor diet can result in a high BMI and therefore the risks associated with being overweight. The use of controlled substances, such as smoking, can result in increased chances of asthma, cancer, and cardiovascular disease (Farhud, 2015). Preventative behaviors are also linked to better health. The Center for Disease Control and Prevention (2017) suggests that regular exercise is linked to many health benefits, such decreased risk of cardiovascular disease, Type 2 diabetes, and even some types of cancer. Accounting for these additional health factors is essential when examining the link between stress and illness symptomatology.

Overview and hypotheses

When studying physical illness symptoms, past research has focused primarily on only one type of stress factor, typically testing only main effects, and not accounting for additional predictors of health. It is important to identify which type of stress factor (or an interaction among them) has the strongest link to physical illness. It is also important to account for other health variables that are linked to both stress and physical illness. Past research has not yet distinguished among stress factors in the same study while also accounting for other health factors. Therefore, we examined the unique role of stress factors on physical illness in three studies. In Study 1, we examined negative affect and perceived stress. In Study 2, we examined neuroticism and perceived stress, and we examined all three stress factors in Study 3. We hypothesized that each stress factor is a unique predictor of physical illness symptomology, and that these associations remain while accounting for other health variables. In accordance with past studies (e.g., Brown & Moskowitz, 1997), we also included exploratory tests of their interaction effects.

Study 1

For Study 1, we tested the hypothesis that both negative affect and perceived stress uniquely predict physical illness, and we tested for the interaction effect between negative affect and perceived stress. We also expected these effects to remain while controlling for other health measures.

Method

Participants and procedure

Participants were 271 introductory psychology students at a mid-south University who participated in exchange for course completion credit. Any participants who were outliers on any of the measures (z-scores > 3.00) were excluded. This resulted in a final sample of 266 participants, most of which was female (n = 228, 86%), Caucasian (n = 245, 93%) and college-aged (65% were between the ages of 18-22; M = 24.23 years). Data were collected through an online system, SONA.

Measures

All variables were assessed in the online questionnaire. Descriptive and reliability statistics are listed below.

Negative affect

The Positive and Negative Affect Schedule (PANAS; see Watson et al., 1988 for psychometric properties) was used to measure participants’ tendency to experience Positive Affect (e.g., “attentive”) and Negative Affect (e.g., “anxious”). The mean of the ratings of the items within the Negative Affect subscale was obtained to produce the Negative Affect score (M = 2.13, SD = 0.67, α = 0.86).

Perceived stress

The Perceived Stress Scale (PSS; Cohen et al., 1983) measures individuals’ sense of personal control over daily life stressors. The scale correlates strongly with depression and physical symptomatology (rs = .70 and .65, respectively). Participants were asked to indicate how often they felt a certain way during the past 2 weeks by finishing the sentence “In the past 2 weeks, how often have you …” with each item. Participants rated items on a 5- point scale (1 = never, 5 = very often). An item example is “… been upset because of something that happened recently.” The mean of the ratings across items was used to create the Perceived Stress score (M = 2.70, SD = 0.57, α = 0.84).

Illness symptoms

An adapted version of the inventory of physical symptoms (Reifman et al., 1991) was used to measure physical health. This measure has demonstrated high internal consistency and test-retest reliability. Participants used a 5-point scale (1 =never, 5 = more than once a day) to rate the frequency during the past month they had experienced physical symptoms, such as “cold or flu,” “chest pains,” and “nausea.” The mean of their responses was calculated to create the Illness Symptoms score (M = 1.86, SD = 0.55, α = .78).

Exercise

An adapted version of a simple method to assess exercise behavior (Godin & Shephard 1985) was used to assess exercise. Participants used a 5-point Likert scale (1 = never, 5 = more than once a day) to rate the frequency during the past month they had partaken in certain exercise activities. Examples of questions included strenuous exercise (heart beats rapidly) such as running, moderate exercise (not exhausting) such as tennis, and mild exercises such as yoga. The sum of the ratings was obtained, then it was standardized to create the Exercise score.

Health food

Participants also completed a scale to measure health food consumption (α = .85). A 5-point Likert scale (1 =never, 5 = more than once a day) was used to rate the frequency in the past month the individual consumed foods such as whole grain breads and fresh vegetables. The sum of the ratings was obtained, then it was standardized to create the Health Food score.

Junk food

Participants then completed a scale to measure junk food consumption. A 5-point Likert scale (1 =never, 5 = more than once a day) was used to rate the frequency the individual consumed foods such as soda and ice cream in the past month. The sum of the ratings was obtained, then it was standardized to create the Junk Food score.

Substance use

Participants next completed a scale to measure their use of illicit substances. A 5-point Likert scale (1 =never, 5 = more than once a day) was used to rate the frequency in the past three months the individual used substances such as alcohol and marijuana. The sum of the ratings was obtained, then it was standardized to create the Substance Use score.

Body mass index

Participants also reported their height in inches and weight in pounds, which was used to calculate their body mass index.

Results and discussion

A preliminary series of bivariate correlations demonstrated that Negative Affect was positively associated with Perceived Stress (r = .64, p < .01). Both stress factors were also positively associated with Illness Symptoms (rs = .52 and .49 for Negative Affect and Perceived Stress, ps < .01).

We tested the hypothesis that negative affect and perceived stress would uniquely predict physical illness symptoms. We also tested for the interaction effect. To test these effects, a hierarchical liner regression was conducted with the centered (score – mean) Negative Affect and Perceived Stress scores entered into Block 1, and their interaction term entered into Block 2, with the Illness Symptom scores entered as the dependent variable. In support of the main hypothesis, there were significant main effects of Negative Affect and Perceived Stress on Illness Symptoms (see Table 1). Negative Affect was a moderate predictor of symptoms, whereas Perceived Stress was a weak-to-moderate predictor. The results did not, however, reveal a significant Negative Affect × Perceived Stress interaction effect.

Table 1.
Hierarchical regression analysis for negative affect and perceived stress predicting illness symptoms.

Variables B SE B β

Step 1

Negative Affect 0.29 0.06 .35

Perceived Stress 0.25 0.06 .26

Step 2

Negative Affect 0.30 0.06 .36

Perceived Stress 0.26 0.07 .27

Negative Affect × Perceived Stress −0.02 0.06 −.02

Step 3

Negative Affect 0.30 0.06 .36

Perceived Stress 0.23 0.07 .23

Negative Affect × Perceived Stress −0.03 0.10 −.03

BMI 0.01 0.00 .11*

Exercise −0.02 0.01 −.16**

Junk Food 0.01 0.01 .09

Health Food 0.01 0.00 .12*

Substance Use 0.00 0.01 .02

Note. **p < .01, p < .05. R² = 0.32, p < 0.01 for Step 1; ΔR²* = 0.00 for Step 2 ns; ΔR² = 0.05 for Step 3 p < .01.

Results from Study 1 confirmed that negative affect and perceived stress both predict physical illness, with negative affect being the strongest predictor. Negative affect is only one type of stress factor, one that has been defined both as a chronic trait and situational state. Study 2 aimed to establish a relationship between a clearly defined trait, neuroticism, and perceived stress in relation to illness symptoms.

Study 2

Study 2 aimed to replicate the relationships between forms of stress and physical illness by examining neuroticism as an alternative indicator type of stress. As was the case in Study 1, we tested the hypothesis that both stress factors uniquely predict physical illness, and we also tested for the interaction effect. In replication of Study 1, we expected these effects to remain while controlling for other health measures.

Method

Participants and procedure

Participants were 577 introductory psychology students at a mid-south University who participated in exchange for course completion credit. Any participants who were outliers on any of the measures (z-scores > 3.00) were excluded. This resulted in a final sample of 543 participants, most of which was female (n_f = 386, 71%), Caucasian (n_c = 501, 92%) and college-aged, although slightly younger than the sample in Study 1 (84% were between the ages of 18-22; M = 20.43 years). Data were collected through the same online system as in Study 1.

Measures

The same measures of Perceived Stress (M = 2.86, SD = 0.52, α = 0.80), Illness Symptoms (M = 1.95, SD = 0.53, α = 0.81), Exercise, Health Food, Junk Food, Substance Use and Body Mass Index (M = 25.15, SD = 5.63) that were used in Study 1 were used again in Study 2.

Neuroticism

To assess participants’ personality traits, they completed a 25-item version of the Big 5 personality measure (John, 1989). Participants rated single words or phrases (e.g., affectionate, competitive, etc.) based on how self-descriptive they were on a 5-point scale (1 = not at all descriptive of me, 5 = extremely descriptive of me). The mean ratings across the five neuroticism items were obtained to create the Neuroticism score (M = 2.98, SD = 0.81, α = 0.80).

Results and discussion

A preliminary series of bivariate correlations demonstrated that Neuroticism and Perceived Stress were positively linked (r = .45, p < .01). All both stress factors were also positively associated with Illness Symptoms (rs = .32 and .42 for Neuroticism and Perceived Stress, ps < .01).

We tested the hypothesis that both neuroticism and perceived stress uniquely predict physical illness symptoms (as well as their interaction effect), we utilized the same analytic procedure as in Study 1. In support of the hypothesis, the results revealed significant main effects of both Neuroticism and Perceived Stress. Neuroticism was a weak predictor of Symptoms, where Perceived Stress was a moderate predictor. Unlike Study 1, however, this was qualified by a significant interaction effect (see Table 2). Simple slopes analysis showed that the positive relation between Neuroticism and Illness Symptoms was stronger at high levels of Perceived Stress (β_HighStress = .21, p < .01) than at low levels of Perceived Stress (β_LowStress = .12, p < .01).

Table 2.
Hierarchical regression analysis for neuroticism, perceived stress, and other health factors.

Variables B SE B β

Step 1

Neuroticism 0.11 0.03 .17

Perceived Stress 0.36 0.04 .35

Step 2

Neuroticism 0.11 0.03 .17

Perceived Stress 0.34 0.04 .33

Neuroticism × Perceived Stress 0.11 0.04 .10*

Step 3

Neuroticism 0.10 0.03 .16

Perceived Stress 0.31 0.04 .30

Neuroticism × Perceived Stress 0.12 0.04 .11*

BMI 0.01 0.00 .08*

Exercise 0.21 0.07 .14*

Junk Food 0.17 0.04 .16**

Health Food 0.11 0.04 .11*

Substance Use 0.13 0.06 .08*

Note. *p < .05, **p < .01. R² = .20, p < .01 for Step 1; ΔR² = .01, ns for Step 2; ΔR² = .11, p <.01 for Step 3.

Results from Study 2 showed how strong the relationship between neuroticism and perceived stress is when predicting physical illness. Even when the impact of other health factors was accounted for, neuroticism and perceived stress still had a significant association with illness symptoms. Contrary to Study 1, this association also has an additive effect: the link between neuroticism and physical illness is stronger at high levels of state stress. In other words, highly neurotic people may not report illness symptoms unless they also perceive their current stressors as beyond their ability to cope with them. Despite these new insights, the question remains regarding the effects when all three stress factors and their interactions are studied simultaneously. We sought to address this in Study 3.

Study 3

The purpose of Study 3 was to examine the predictive power of the three stress factors on illness symptoms, including their two-way and three-way interactions. As was the case in the two prior studies, we tested the hypothesis that different forms of stress uniquely predict physical illness, and we also tested for all two-way and the three-way interaction effects. We expected these effects to remain while controlling for other health measures.

Method

Participants and procedure

Participants were 300 introductory psychology students at a mid-south University who participated in exchange for course completion credit. As was the case with Studies 1 and 2, most of the sample was female (n_f = 260, 87%), Caucasian (n_c = 256, 86%) and college-aged (75% were between the ages of 18-22; M = 22.23 years). Data were collected through the same online system as in Studies 1 and 2.

Measures

The same measures of Negative Affect (M = 2.48, SD = 0.74, α = .84), Neuroticism (M = 3.49, SD = 0.71, α = .84), Perceived Stress (M = 3.02, SD = 0.51, α = .81), Illness Symptoms (M = 2.18, SD = 0.58, α = .79), Exercise, Health Food, Junk Food, Substance Use and Body Mass Index (M = 27.21, SD = 6.99) that were used in the previous studies were used again in Study 3.

Results and discussion

A preliminary series of bivariate correlations demonstrated that Negative Affect was positively associated with Neuroticism (r = .64, p < .01) and Perceived Stress (r = .69, p < .01), and Neuroticism and Perceived Stress were also positively linked (r = .65, p < .01). All three stress factors were also positively associated with Illness Symptoms (rs = .54, .40 and .42 for Negative Affect, Neuroticism and Perceived Stress, ps < .01).

To test the main and interaction effects of the three stress factors on illness symptoms, a hierarchical liner regression was conducted with the centered Negative Affect, Neuroticism and Perceived Stress scores entered into Block 1, the three two-way interaction terms added in Block 2, the three-way interaction term added in Block 3, and the health covariates entered in Block 4. Illness Symptoms was entered as the dependent variable. The results revealed a significant main effect of Negative Affect, which was a strong predictor of Illness Symptoms, with no other significant main effects or interaction effects (see Table 3).

Table 3.
Hierarchical regression analysis for negative affect, neuroticism, perceived stress, and other health factors.

Variables B SE B β

Step 1

Negative Affect 0.36 0.06 .46

Neuroticism 0.07 0.06 .09

Perceived Stress 0.05 0.08 .04

Step 2

Negative Affect 0.36 0.06 .46

Neuroticism 0.07 0.06 .08

Perceived Stress 0.06 0.08 .05

Negative Affect × Neuroticism 0.05 0.09 .05

Negative Affect × Perceived Stress −0.04 0.11 −.03

Neuroticism × Perceived Stress −0.12 0.13 −.08

Step 3

Negative Affect 0.37 0.06 .46

Neuroticism 0.08 0.06 .10

Perceived Stress 0.07 0.09 .06

Negative Affect × Neuroticism 0.05 0.09 .05

Negative Affect × Perceived Stress −0.01 0.12 −.01

Neuroticism × Perceived Stress −0.14 0.13 −.09

Negative Affect × Neuroticism × Perceived Stress −0.06 0.09 −.05

Step 4

Negative Affect 0.34 0.06 .44

Neuroticism 0.08 0.06 .09

Perceived Stress 0.09 0.09 .08

Negative Affect × Neuroticism 0.01 0.09 .01

Negative Affect × Perceived Stress 0.03 0.11 .02

Neuroticism × Perceived Stress −0.12 0.13 −.08

Negative Affect × Neuroticism × Perceived Stress −0.05 0.09 −.05

BMI 0.01 0.00 .13**

Exercise 0.01 0.01 .05

Junk Food 0.01 0.01 .06

Health Food 0.01 0.00 .12*

Substance Use 0.01 0.01 .05

Note. *p < .05, **p < .01. R² = .30, p < .01 for Step 1; ΔR² = .01, ns for Step 2; ΔR² = .00, ns for Step 3, ΔR² = .05, p < .01 for Step 4.

The results from Study 3 demonstrated that negative affect was the only unique predictor of physical illness among the three stress factors. Unlike the previous studies, we accounted for the high multicollinearity across all three stress factors, which likely explains the discrepancies from the previous studies. This suggests that negative affect may be the primary stress factor linked to physical illness.

General discussion

The main objective of our research was to examine how three forms of stress uniquely physical illness symptomatology while accounting for other common predictors of health. The results across the three studies offered consistent evidence that the stress factors contribute to a large amount of variance in reporting illness symptoms, above and beyond their interactions and alternative predictors of poor health. The degree to which the stress factors linked to this outcome, however, differed across the studies. Studies 1 and 2 demonstrated that perceived stress predicted illness symptoms, and Study 2 demonstrated that neuroticism also predicted illness symptoms when paired with perceived stress. Negative affect also emerged as a significant predictor in Study 1, and it was the only significant predictor in Study 3. Taken together, these results suggest that the stress factors are highly connected with each other, and that negative affect is the most reliable predictor of illness symptomatology.

Implications

These results lend further support to past research showing that negative affect explains more variability in health outcomes than alternative stress factors (De Gucht et al., 2004). This may be due to people with high levels of negative affect being more sensitive to their symptoms (Cameron et al., 1998, and more inclined to report symptoms during significant life events than others (McAndrew et al., 2014).

The assessment of both neuroticism and negative affect in Study 3 addressed a common concern about the conflation of these two constructs in stress research. The definitions are notably similar; being neurotic is the tendency to experience more negative emotions and distress, whereas negative affect is the tendency to have feelings of anger, scorn, disgust, and overall subjective distress (Watson & Pennebaker, 1989). This conceptual overlap was also manifested in the high multicollinearity among the three stress factors, further necessitating the need to account for their covariation. Our results demonstrated that the subcomponents of neuroticism that relate to negative affect may be the main factor that links the trait to higher incidences of physical illness. In contrast, the impulsiveness, self-consciousness, and vulnerability subcomponents that compose neuroticism may not be linked to illness.

The relatively weaker link between neuroticism and illness symptoms also corresponds with past research (e.g., Brown & Moskowitz, 1997). The interaction between neuroticism and perceived stress in Study 2 further demonstrates that neurotic individuals are not susceptible to poorer health outcomes unless they are currently experiencing stressful events. This may be because highly neurotic people show higher reactivity to stressful events than others (Gunthert et al., 1999; Schneider et al., 2012; Vollrath, 2001). Based on neuroticism’s lack of predictive power in Study 3, that reactivity may be explained by its link to negative affect.

Our results also expand upon past research in several ways. A multitude of studies in the past have examined stress and how it relates to physical illness. However, research has examined all three of these stress factors independently, nor their interactions, nor while also accounting for common health covariates. Looking at the stress factors independently allowed us to determine which was the strongest predictor of physical illness. We also demonstrated that neuroticism and negative affect, though similar, are not linked to physical illness in the same way. Based on our results, people with high negative affect will report more illness symptoms regardless of the presence of environmental stressors, whereas highly neurotic people will only report more stressors than others when they are currently stressed, and this may ultimately be explained by their higher tendency toward negative affect.

Limitations and future directions

One major limitation of both studies was the reliance on self-report data. Although self-report is a quick and easy way to get a lot of data, people’s subjective reports of themselves can be biased or answers may be inaccurate based on many factors, such as their current mood and length of the questionnaire. This poses a problem for all three studies. To avoid this in future research, less subjective reports of stress and health could be provided by trained professionals to get a more accurate representation of the individual’s stress and health.

The samples across the three studies were also limited. All three studies used a mid-south university to obtain their data, meaning that the samples were mostly Caucasian, female college students who were seeking course credit. Although college student samples provide estimates comparable to the rest of the adult population (see King et al., 2004 for a review), stress responses differ across gender and ethnic groups (e.g., Attell et al., 2017), which constrains how well these results can be generalized to males and ethnic minorities. Future research should therefore account for these differences across the three stress factors. Furthermore, a longitudinal study would provide a data set that included an individual’s state- and trait-level versions of the stress factors over time and their symptomatology associated with each under a variety of circumstances.

The three studies also mostly sampled young adults, which limits the ability to examine chronic conditions and other long-term health problems. For future studies, multiple age groups could be examined to determine how people at different ages report their symptoms. Socioeconomic diversity would also be a necessity for future applications of this research. Conway (2016) identified socioeconomic status as the most important tool available when determining disease and injury. Such demographic considerations should be prioritized in future research.

Conclusion

Across three studies, we examined three different types of stress and how each contributes to reporting physical illness. Although there were some instances where all three seemed to link to symptom reporting, we found that negative affect was the primary predictor of it. By focusing on treatments that reduce negative affect in particular, the incidences of both temporary and chronic illness may be lowered considerably.

Variables	B	SE B	β
Step 1
Negative Affect	0.29	0.06	.35**
Perceived Stress	0.25	0.06	.26**
Step 2
Negative Affect	0.30	0.06	.36**
Perceived Stress	0.26	0.07	.27**
Negative Affect × Perceived Stress	−0.02	0.06	−.02
Step 3
Negative Affect	0.30	0.06	.36**
Perceived Stress	0.23	0.07	.23**
Negative Affect × Perceived Stress	−0.03	0.10	−.03
BMI	0.01	0.00	.11*
Exercise	−0.02	0.01	−.16**
Junk Food	0.01	0.01	.09
Health Food	0.01	0.00	.12*
Substance Use	0.00	0.01	.02

Variables	B	SE B	β
Step 1
Neuroticism	0.11	0.03	.17**
Perceived Stress	0.36	0.04	.35**
Step 2
Neuroticism	0.11	0.03	.17**
Perceived Stress	0.34	0.04	.33**
Neuroticism × Perceived Stress	0.11	0.04	.10*
Step 3
Neuroticism	0.10	0.03	.16**
Perceived Stress	0.31	0.04	.30**
Neuroticism × Perceived Stress	0.12	0.04	.11*
BMI	0.01	0.00	.08*
Exercise	0.21	0.07	.14*
Junk Food	0.17	0.04	.16**
Health Food	0.11	0.04	.11*
Substance Use	0.13	0.06	.08*

Variables	B	SE B	β
Step 1
Negative Affect	0.36	0.06	.46**
Neuroticism	0.07	0.06	.09
Perceived Stress	0.05	0.08	.04
Step 2
Negative Affect	0.36	0.06	.46**
Neuroticism	0.07	0.06	.08
Perceived Stress	0.06	0.08	.05
Negative Affect × Neuroticism	0.05	0.09	.05
Negative Affect × Perceived Stress	−0.04	0.11	−.03
Neuroticism × Perceived Stress	−0.12	0.13	−.08
Step 3
Negative Affect	0.37	0.06	.46**
Neuroticism	0.08	0.06	.10
Perceived Stress	0.07	0.09	.06
Negative Affect × Neuroticism	0.05	0.09	.05
Negative Affect × Perceived Stress	−0.01	0.12	−.01
Neuroticism × Perceived Stress	−0.14	0.13	−.09
Negative Affect × Neuroticism × Perceived Stress	−0.06	0.09	−.05
Step 4
Negative Affect	0.34	0.06	.44**
Neuroticism	0.08	0.06	.09
Perceived Stress	0.09	0.09	.08
Negative Affect × Neuroticism	0.01	0.09	.01
Negative Affect × Perceived Stress	0.03	0.11	.02
Neuroticism × Perceived Stress	−0.12	0.13	−.08
Negative Affect × Neuroticism × Perceived Stress	−0.05	0.09	−.05
BMI	0.01	0.00	.13**
Exercise	0.01	0.01	.05
Junk Food	0.01	0.01	.06
Health Food	0.01	0.00	.12*
Substance Use	0.01	0.01	.05

Footnotes

Article Notes

ORCID iD

Rebecca Barron

References

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I. S.

(2016). The role of neuroticism in the maintenance of chronic baseline stress perception and negative affect. The Spanish Journal of Psychology, 19, 1–9.

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