A prospective cohort study on symptoms of common mental disorders among Dutch elite athletes

ABSTRACT

Objective: Scientific knowledge about symptoms of common mental disorders in elite sports is scarce. Consequently, the objectives of the study were to (i) establish the 12-month incidence of symptoms of common mental disorders (CMD; distress, anxiety/depression, sleep disturbance, adverse alcohol use, eating disorders) among Dutch elite athletes and (ii) explore their potential association with several stressors (being injured, recent life events, career dissatisfaction).

Methods: A prospective cohort study with a 12-month follow-up period was conducted. The study used validated questionnaires to assess symptoms of common mental disorders (thus not clinically diagnosed) as well as several stressors; an electronic questionnaire was set up and repeatedly distributed.

Results: A total of 203 elite athletes gave their written informed consent to participate in the study, from which 143 completed the 12-month follow-up period (follow-up rate of 70%). Incidence of symptoms of CMD ranged from 6% for adverse alcohol use to 57% for symptoms of anxiety/depression. Over the follow-up period, around 17% of the participants reported two simultaneous symptoms of CMD, and around 19% reported three simultaneous symptoms of CMD. Inferences between some stressors and symptoms of CMD were found but none of the associations were statistically significant.

Conclusions: Substantial 12-month incidence rates of symptoms of CMD (self-reported and not clinically diagnosed) were found among Dutch elite athletes (especially for anxiety/depression), appearing similar to the ones found among athletes from other sports disciplines and the Dutch general population. Also, inferences between some stressors and symptoms of CMD were found but none of the associations were statistically significant. Supportive and preventive measures directed towards symptoms of CMD should be developed to improve awareness and psychological resilience of athletes, which would likely improve their performance and quality-of-life.

KEYWORDS:

• Sports
• mental disorders
• epidemiology
• athletes

1. Introduction

Over the past few years, attention to symptoms of distress (overstressed), anxiety, depression, or adverse substance use – typically referred as symptoms of common mental disorders (CMD) – among professional athletes has been growing [1,2]. Among professional footballers (soccer), prevalence of symptoms of CMD ranged from 9% for adverse alcohol use to 38% for anxiety/depression, while 12-month incidence reached up to 37% for anxiety/depression [3,4]. Among elite Gaelic athletes, prevalence and 6-month incidence reached up to 48 and 21% for anxiety/depression, respectively, while around 24% reported 2 simultaneous (comorbidity) symptoms of CMD [5]. Among professional rugby players, prevalence of symptoms of CMD ranged from 15% for adverse alcohol use to 30% for anxiety/depression, almost 20% of these participants reporting a comorbidity of two simultaneous symptoms of CMD [6]. Among professional ice hockey players, prevalence of symptoms of CMD ranged from 8% for adverse alcohol use to 24% for anxiety/depression, while 6-month incidence reached up to 22% for eating disorders [7]. In these aforementioned studies, the occurrence of symptoms of CMD was shown to be related with several stressors among which were musculoskeletal injuries, recent life events, and career dissatisfaction [3–7].

Among Dutch elite athletes, the 4-week prevalence of symptoms of CMD ranged from 6% for adverse alcohol use to 45% for anxiety/depression [8]. By contrast to football, Gaelic sports, rugby and ice hockey, empirical information collected longitudinally about the incidence (newly developed) of symptoms of CMD among elite Dutch athletes drawn from multiple sports is not available yet, while these symptoms are likely to be associated with similar stressors. Accordingly, the objectives of the study were to (i) establish the 12-month incidence and comorbidity of symptoms of CMDs (distress, anxiety/depression, sleep disturbance, adverse alcohol use, eating disorders) among Dutch elite athletes and (ii) explore their potential association with several stressors (being injured, recent life events, career dissatisfaction).

2. Methods

2.1. Design

Reported in compliance with the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement, the present study was an observational prospective cohort study with three measurements over a follow-up period of 12 months by means of questionnaires [9]. Ethical approval was provided by the Medical Ethics Review Committee of the Academic Medical Center (W15_051#15.0062; Amsterdam, The Netherlands). The present research was conducted in accordance with the Declaration of Helsinki [10].

2.2. Study setting, participants and sample size

Participants were Dutch elite athletes from the Netherlands Olympic Committee*Netherlands Sports Confederation (NOC*NSF). NOC*NSF is the Dutch association which provides financial, material, performance, and social advice and support to both current and former elite athletes. Elite athletes from NOC*NSF are committing significant time to elite sports and are competing at international or highest national sporting level (eligible for Olympic Games and national teams competitions). Inclusion criteria for the participants were: (i) being on the NOC*NSF list of official elite athletes; (ii) being aged 18 years or older; and (iii) being fluent in Dutch. With regard to the first aim of the study, sample size calculation indicated that at least 130 athletes were required (power of 80%; confidence interval (CI) of 95%; precision of 5%) under the assumption that one out of five athletes might suffer from a symptom of CMD [11]. Expecting a baseline response rate of around 40% and a loss to follow-up at 50% (based on previous similar studies in other sports), we intended to invite at least 620 Dutch elite athletes.

2.3. Dependent variables: symptoms of CMDs

Symptoms of distress, anxiety/depression, sleep disturbance, adverse alcohol use, and eating disorders were measured at baseline (presence/absence in previous four weeks) and during the follow up (presence/absence in previous 6 months). Distress was measured using the Distress Screener (3 items scored on a 3-point scale) which is based on the four-dimensional symptom questionnaire (4DSQ) (e.g. ‘Did you recently suffer from worry?’) [12,13]. The 4DSQ i.e. Distress Screener has been validated in several languages among which Dutch (internal consistency: 0.6–0.7; test-retest coefficients: ≥ 0.9; criterion-related validity: sensitivity 0. 8, specificity 0.7, Area Under ROC Curve ≥0.8) [12,13]. A total score ranging from 0 to 6 was obtained by summing up the answers on the three items, a total score of 3 or less indicating the absence of distress and a total score of 4 or more indicating the presence of distress [12,13]. The 12-item General Health Questionnaire (GHQ-12) was used to assess psychological symptoms related to anxiety/depression (e.g. ‘Have you recently felt under strain?’) [14]. The GHQ-12 has been validated in several languages among which Dutch (internal consistency: 0.7–0.9; criterion-related validity: sensitivity 0.8, specificity 0.8, Area Under ROC Curve ≥0.8) [14]. Based on the traditional scoring system, a total score ranging from 0 to 12 was calculated by summing up the answers on the 12 items, with a score of 2 or less indicating no signs of anxiety/depression and a score of 3 or more indicating signs of anxiety/depression (Area Under Curve = 0.9) [14]. Based on the PROMIS (short form), sleep disturbance was assessed through four single questions (e.g. ‘Did you recently have some problem to sleep?’) scored on a 5-point scale (from ‘not at all’ to ‘very much’) [15]. The PROMIS has been validated in several languages among which Dutch (internal consistency: >0.9; construct validity: product-moment correlations ≥0.9) (for detailed information, see www.nihpromis.org). A total score ranging from 1 to 20 is obtained by summing up the answers to the four questions, a score of 12 or less indicating the absence of sleep disturbance and a score of 13 or more indicating the presence of sleep disturbance [15]. Level of alcohol consumption was detected using the 3-item AUDIT-C (e.g. ‘How many standard drinks containing alcohol do you have on a typical day?’) [16]. The AUDIT-C has been validated in several languages among which Dutch (test-retest coefficients: 0.6–0.9; criterion-related validity: sensitivity 0.8, specificity 0.8, Area Under ROC Curve ≥0.7) [17]. A total score ranging from 0 to 12 was obtained by summing up the answers on the three items, a score of 4 or less indicating the absence of adverse alcohol use, and a score of 5 or more indicating the presence of adverse alcohol use [16,17]. The Eating disorder Screen for Primary care (5-items scored as ‘yes’ or ‘no;’ ‘0’ for favorable answer, ‘1’ for unfavorable answer) was used as a screening instrument to detect eating disorders (e.g. ‘Were you satisfied with your eating patterns?’) [18]. The Eating disorder Screen for Primary care has been validated in several languages among which Dutch (criterion-related validity: sensitivity 1.0, specificity 0.7) [18]. A total score ranging from 0 to 5 is obtained by summing up the answers on the five items, a score of 0 or 1 indicating the absence of eating disorders and a score of 2 or more indicating the presence of eating disorders [18].

2.4. Independent variables: stressors

Being injured, number of recent life events and career dissatisfaction were measured at baseline (and during follow up). The presence of musculoskeletal injury was examined through a single question (yes or no), injury being defined as one that involved the musculoskeletal system (bone, joint, ligament, muscles, tendons) and occurred during training or competition and led to the current training or competition absence (definition being clearly stated to the participants) [19]. Based on the validated Social Athletic Readjustment Rating Scale, the occurrence of life events (e.g. ‘Death of spouse,’ ‘Change in financial state’) in the previous 6 months was explored by 14 single questions (yes or no) [20]. Score was calculated by summing up the life events occurred in the previous 6 months and the sum score was also subsequently transformed into a dichotomous variable: not exposed to recent life event, or exposed to 1 or more recent life events. Elite sport career dissatisfaction was explored through the validated Greenhaus scale (e.g. ‘I am satisfied with the success I have achieved in my career’) (5 items on a 5-point scale) [21]. A total score (5–25) was obtained by summing up the answers to the five items and this sum score was also subsequently transformed as a dichotomous variable: 5–12 as being dissatisfied with elite sport career and 13–25 as being satisfied [21].

2.5. Procedures

Based on the independent and dependent variables included in the study, a baseline and 2 follow-up electronic anonymous questionnaires available in Dutch were created (FluidSurveys^TM), including the following descriptive variables: age, gender, height, weight, type of sport, duration of elite sport career, educational level, employment or study status, and number of working or studying hours. In order to guarantee the strict confidentiality of the responses, no personal identifiable information was included in the questionnaires. Each questionnaire took about 15–20 min to complete. Information about the purpose and procedures of the study was sent per email to potential participants by the medical staff of NOC*NSF. Participants interested in the study, gave their informed consent and were given access to the baseline online questionnaire which they were asked to complete within two weeks. After completion of the baseline questionnaire, participants could give their informed consent for the follow-up questionnaire and leave therefore their email address. At 6- and 12-month follow-up, participants were invited by email to complete the second and third questionnaire within 2 weeks. Reminders at baseline and follow up were sent after 2 and 4 weeks. Once completed, the electronic questionnaires were saved automatically on a secured electronic server that only the principal investigator could access. Participants participated voluntarily in the study and did not receive any reward for their participation. Baseline questionnaires were distributed online between October and December 2015.

2.6. Statistical methods

All data analyses were performed using the statistical software IBM SPSS Statistics 23.0 for Windows. Descriptive data analyses (mean, standard deviation, frequency, range) were performed with the descriptive and independent variables measured at baseline. To explore whether loss to follow up was selective, we compared baseline characteristics (age, height, weight, duration of elite sport career) of nonresponders and responders at follow up by means of independent T-tests [11]. The 12-months incidence and comorbidity of symptoms of CMD in the whole group of participants were calculated over the follow-up period of 12 months, using the adjusted Wald method (incidence: sample size of 150 persons or less) for 95% confidence intervals (95% CI) [11]. Incidence (expressed as a percentage) was calculated as the proportion of the number of participants with a newly given symptom of CMD during the 12-months follow-up relative to the total number of players without any symptom of CMD at baseline [11]. Comorbidity of two, three, four, or five simultaneous symptoms of CMD was defined as the simultaneously presence of two, three, four, or five symptoms of CMD (respectively) among the participants. Comorbidity was expressed as a percentage and calculated as the proportion of the number of participants with newly developed two, three, four, or five simultaneous symptoms of CMD during the 12-month follow-up relative to the total number of players without any symptom of CMD at baseline. The relative risks (RR) and related 95% CI were calculated to explore the strength of the association between potential baseline stressors and the onset of symptoms of CMD (dichotomous dependent variable) during the subsequent 12-month follow up [11].

3. Results

3.1. Participants

A total of 726 elite athletes were contacted for the study by NOC*NSF, from which 203 gave their written informed consent to participate in the study (response rate of 28%). After the follow-up period of 12 months, a total of 143 athletes had completed the follow up (follow-up rate of 70%). The flowchart of the recruitment of the participants is presented in Figure 1. The mean age of the participants at baseline (36% male; 64% female) was 27 years (SD = 7), and they had been active in elite sport for eight years on average (SD = 5; 48% in team sports; 52% in individual sports). All characteristics of the participants (total cohort and subgroups) are presented in Table 1.

Table 1. Baseline characteristics of the Dutch elite athletes.

	Total (N = 203)	No CMD (N = 74)	CMD (N = 129)
Age (in years; mean ± SD)	27 ± 7	26 ± 6	28 ± 8
Male/Female (%)	36/64	38/62	34/66
Height (in cm; mean ± SD)	177 ± 10	179 ± 10	177 ± 10
Weight (in kg; mean ± SD)	71 ± 13	71 ± 13	71 ± 13
Duration of elite sport career (in years; mean ± SD)	8 ± 5	7 ± 5	8 ± 5
Team/Individual sport (%)	48/52	43/57	50/50
Educational level (%)
No schooling completed	2	3	1
Nursery/Elementary school	1	0	2
High school	7	9	6
Vocational/technical school	34	35	32
College, university or equivalent	56	53	59
Currently working or studying (%)	49	50	50
Working/studying hours per week (in hours; mean ± SD)	17 ± 14	18 ± 15	16 ± 13
One or more severe injuries (%)	64	60	65
One or more surgeries (%)	31	26	34
One or more recent life events (%)	72	65	82
Career dissatisfaction (%)	31	18	36
Baseline prevalence (%)
Distress	27
Anxiety/depression	45
Sleep disturbance	22
Adverse alcohol use	6
Eating disorders	32

N: number of participants; no CMD: group without symptoms of common mental disorders at baseline; CMD: group with symptoms of common mental disorders at baseline; SD: standard deviation; cm: centimeters; kg: kilograms; %: percentage

Figure 1. Flowchart of the recruitment and follow-up of Dutch elite athletes.

3.2. Incidence and comorbidity of symptoms of CMDs

The incidence of symptoms of CMD among Dutch elite athletes over the follow-up period of 12 months ranged from 6% for adverse alcohol use to 57% for symptoms of anxiety/depression. Seventeen percent of the participants reported two simultaneous symptoms of CMD over the follow-up period, 19% three simultaneous symptoms of CMD and 3% five simultaneous symptoms of CMD. The 12-month incidence and comorbidity (and related 95% CI) of symptoms of CMD among Dutch elite athletes are presented in Table 2.

Table 2. 12-month incidence of symptoms of common mental disorders among Dutch elite athletes.

	Incidence	(95% CI)
Distress	32.4	(19.6–48.6)
Anxiety/depression	56.8	(40.9–71.3)
Sleep disturbance	19.4	(9.5–35.3)
Adverse alcohol use	5.6	(0.6–19.1)
Eating disorders	16.7	(7.5–32.3)
Comorbidity – 2 symptoms	16.7	(7.5–32.3)
Comorbidity – 3 symptoms	19.4	(9.5–35.3)
Comorbidity – 4 symptoms	0	(0–8.4)
Comorbidity – 5 symptoms	2.8	(<0.1–15.4)

95% CI: confidence interval

3.3. Potential association between stressors and symptoms of CMDs

Some stressors under study inferred with symptoms of CMD. For instance, being injured inferred with symptoms of distress (RR = 2.5; 95%CI = 0.2–45.0) while career dissatisfaction inferred with symptoms of anxiety/depression (RR = 3.5; 95%CI = 0.4–35.5) and symptoms of adverse alcohol use (RR = 7.0; 95%CI = 0.4–138.2). However, none of the associations was found to be statistically significant. All RR and related 95%CI are presented in Table 3.

Table 3. Association (relative risk and 95% CI) between stressors and symptoms of common mental disorders among Dutch elite athletes.

		Distress	Anxiety/Depression	Sleeping disturbance	Adverse alcohol use	Eating disorders
Being injures	No	1.0	1.0	1.0	1.0	1.0
	Yes	2.5 (0.2–45.0)	0.9 (0.5–15.1)	n/a	n/a	n/a
Recent life events	No	1.0	1.0	1.0	1.0	1.0
	Yes	1.5 (0.2–11.0)	1.1 (0.4–3.3)	0.8 (0.2–3.0)	1.6 (0.2–14.5)	0.9 (0.2–4.6)
Career dissatisfaction	No	1.0	1.0	1.0	1.0	1.0
	Yes	0.7 (0.2–2.2)	3.5 (0.4–35.5)	1.0 (0.1–10.3)	7.0 (0.4–138.2)	2.2 (0.2–26.3)

4. Discussion

The main findings of this study were that the 12-month incidence of symptoms of CMD among Dutch elite was 32% for distress, 57% for anxiety/depression, 19% for sleeping disturbance, 6% for adverse alcohol use, and 17% for eating disorders. Over the follow-up period, around 17% of the participants reported two simultaneous symptoms of CMD, and around 19% reported three simultaneous symptoms of CMD. Also, inferences between some stressors and symptoms of CMD were found but none of the associations were statistically significant.

4.1. Comparisons with athletes from other professional i.e. elite sports

Several recent studies using similar scales for measuring symptoms of CMD that we used in our study were conducted among athletes across several professional i.e. elite sports. Among European professional footballers (N = 262) recruited in Finland, France, Norway, Spain, and Sweden, 12-month incidence rates of symptoms of CMD ranged from 12% for distress to 37% for anxiety/depression, while approximately 13% of these participants reported 2 simultaneous symptoms of CMD [4]. In this study, professional footballers reporting recent adverse life events or career dissatisfaction were more likely to report symptoms of CMD, but statistically significant associations were not found [4]. In Gaelic sports (N = 204), 6-month incidence of symptoms of CMD ranged from 11% for sleep disturbance to 21% for anxiety/depression, while severe musculoskeletal injury, recent life events and career dissatisfaction led to an increased risk for symptoms of CMD [5]. In South African professional cricket (N = 78), 6-month incidence of symptoms of CMD over the follow-up period ranged from 9% for distress to 15% for anxiety/depression, sleep disturbance, and adverse alcohol use [22]. In professional ice hockey (N = 81), the incidence of symptoms of CMD over a follow-up period of 6 months ranged from 6% for distress and adverse alcohol use to 22% for eating disorders [7]. In this study, professional ice hockey players exposed to a higher number of recent life events and/or higher level of career dissatisfaction were found to be 5 times more likely to report symptoms of CMD by comparison to those less or unexposed [7]. Despite some trivial differences, most incidence rates of symptoms of CMD found in our study among Dutch elite athletes are similar to those found among professional i.e. elite athletes from other sports disciplines. This concurs with our expectations as professional i.e. elite athletes, are, regardless their sport discipline, exposed during their careers to similar stressors that might lead to symptoms of CMD [23,24]. Only the incidence of symptoms of anxiety/depression is higher than in other sports. A potential explanation is the gender distribution of our study population (one-third males and two-thirds females) as females are more likely to suffer from anxiety/depression than males [1,2]. Another explanation is that our follow-up study was conducted in the year of the Olympic Games in Rio (Brazil), such an important event being more likely to bring to most athletes anxious moments (qualification or not) and disappointments (no medals) rather than positive moments. However, such potential explanation cannot be underpinned by our study.

4.2. Comparisons with the Dutch general population

In the Netherlands, the Mental Health Survey and Incidence Study (NEMESIS) showed that the 12-month prevalence for mood, anxiety, and substance use disorders reached up to 10% [25]. However, a valid comparison of these results with ours cannot be made because NEMESIS referred to the prevalence of CMD [25]. Even more, NEMESIS used other instruments (interview, namely the Composite International Diagnostic Interview) to establish the presence of CMD than those we used in our study, making any comparison invalid and biased [25].

4.3. Methodological considerations

Four main methodological considerations of the present study should be mentioned. First, as the recruitment procedures were blinded to the research team for privacy and confidentiality reasons (participants invited by NOC*NSF), a nonresponse analysis could not be conducted. Second, participants (as in any scientific study) were free to be included in the study and thus self-selected. This might have led to selection bias as participants with more interest with symptoms of CMD might have been more likely to participate. Third, the response rate achieved in our study at baseline (28%) was lower than expected, while a good follow-up rate (70%) was secured. The low response rate at baseline might limit the representativeness of our results, confirming once more that a study in professional i.e. elite sports about symptoms of CMD including a large study sample remains challenging to conduct. Last, the dependent variables in our study were measured through self-report. Consequently, it is essential to mention that the occurrence of self-reported symptoms of CMD was studied but not the presence of clinically diagnosed CMD. While one might suggest that the validity of self-reported data might be limited, the importance and relevance of Patient Reported Outcome Measures (PROMs) studies has been lately empowered in clinical and sports medicine in order to assess the aspects that matter most to patients and to enable important clinical questions to be answered [26]. Also, the self-report instruments used in our study were validated in Dutch and not too extensive (influencing negatively internal consistency) in order to secure adherence of the participants in our study.

4.4. Practical implications

Our study contributes largely to raise self-awareness about symptoms of CMD in professional, i.e. elite sports as epidemiological information on symptoms of CMD in sports remains scarce [27]. Contradictory to our a-priori hypotheses, we did not find any statistically significant association between the stressors under study and our outcome measures. Nevertheless, monitoring the occurrence of stressors such as injuries, life events, or career transitions among elite athletes during their sport career should remain one of the priority of the technical, medical, and psychological/behavioral teams around the athletes [28,29]. The authors believe that this is even more important before and after an important event such as the Olympic Games. Such a monitoring should enable to identify athletes being predisposed to report symptoms of CMD and refer them timely to proper medical care and support. Our study empowers also the current assertive approach of NOC*NSF that relies on supportive and preventive measures directed toward symptoms of CMD among Dutch athletes. Such an approach is key in order to protect the health of elite athletes and empower their performances as well as their quality of life.

5. Conclusions

Substantial 12-month incidence rates of symptoms of CMD (self-reported and not clinically diagnosed) were found among Dutch elite athletes (especially for anxiety/depression), appearing similar to the ones found among athletes from other sports disciplines and the Dutch general population. The occurrence of symptoms of CMD inferred with being injured, recent life events, and career dissatisfaction but none of these associations were statistically significant. Supportive and preventive measures directed toward symptoms of CMD should be developed to improve not only awareness and psychological resilience of athletes but also their performance and quality of life.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Acknowledgment

The authors would like to thank the Athletes Committee and medical staff of the Netherlands Olympic Committee*Netherlands Sports Confederation (NOC*NSF) for their support in the study (especially former elite athlete Margriet de Schutter and Olympic champions Stefan Groothuis and Mieke Cabout). We are grateful to all the elite athletes who participated in the study.

Additional information

Funding

This study was not funded.