Introduction

A low prevalence of psychiatric disorders in athletes was assumed for a very long time, both by health professionals and by the general public. This mis-assumption might have stemmed from an overall cultural inclination to idealise athletes and their health, thereby foreclosing the possibility of their having psychiatric illnesses. Athletes themselves were taught to be tough and to focus on physical performance and physical signs interfering with optimal capacity at the expense of mental symptoms. Relatedly, mental disorders in general, and in particular among upper-level athletes, are stigmatised, and this situation is perpetuated by the general public and the media, as well as by sport clubs and health professionals. This has led to a paucity of research and an underdevelopment of specific psychiatric treatment facilities for athletes. In 2010, Hoyer and Kleinert [23] pondered the question of whether it was justified to describe athletes as super healthy people with above-average authority expectations and increased resistibility. The broad neglect of the mental symptoms of professional athletes, as well as of their need for specific treatment facilities, led unfortunately to a rather general transferral rate of athletes to mental health service providers. Health consequences due to delayed diagnosis and a lack of adequate therapy had to be paid by the athletes themselves.

In addition to sport psychology, which focuses mainly on performance enhancement, sport psychiatry deals with diagnosis and treatment of psychiatric illnesses in athletes while taking the diagnostic and therapeutic issues unique to this population into account. Glick and Horsfall [17] suggested three main reasons for a specific treatment of athletes. First, the state of mind of an athlete has a significant impact on his or her performance. Second, participation in sports affects a person’s mood, thinking, personality and health. And third, psychiatric care of the athlete must be adapted to the athletic context.

It is important to realise that the above-described social landscape vis-à-vis the mental health of athletes delayed the appropriate development of sport psychiatry until very recently. But, observations in this arena are by no means new: already in 1932, Jokl and Guttmann [26] described neurologic–psychiatric symptoms of a boxer which could have initiated the development of sport psychiatry. This review will focus on the specific character of mental disorders in high-performance athletes and the consequences this has for research and treatment. It is beyond the scope of this article to give a comprehensive review of all issues raised. We focussed, therefore, on the sport-related issues of eating disorders (ED), exercise addiction, dementia pugilistica and mood disorders in context of overtraining syndrome (OTS).

Eating disorders

ED among athletes has been relatively well studied. The two most common are anorexia nervosa, which is characterised by a refusal to maintain a minimally normal bodyweight and bulimia nervosa, which involves repeated episodes of binge-eating followed by inappropriate compensatory behaviours, such as self-induced vomiting, food restriction, or excessive exercise. It is well known that the incidence of ED is strongly gender-dependent. Calhoun et al. [12] reported an incidence of ED in female athletes of as high as 60 %. They found these cases to be mostly associated with long-distance running, gymnastics and figure skating (the so-called leanness sports). For instance, Byrne and McLean [11] reported a 15 % prevalence of ED among female athletes practicing leanness sports, 2 % for athletes taking exercises in non-leanness sports and 1 % among non-athlete controls. Only 5 % of male athletes in leanness sports were found to show signs of ED compared with an occurrence rate of zero in men practicing non-leanness sports and among male controls.

Anorexia athletica

Not only did practitioners of aesthetic sports and leanness sports show a much higher rate of clinical ED, but they were also found to suffer from atypical or subclinical ED [5, 25, 43, 52, 54]. The incidence of at least one eating disorder-related criterion was reported in as high as 73.6 % of athletes of different sports [44]. It is important to realise that athletes show eating patterns or activity levels which may be reminiscent of “anorexic-like” behaviour, but do not technically fulfil the minimal diagnostic criteria [52]. Therefore, Pugliese et al. [41] coined the term “anorexia athletica” (AA) in 1983 to refer to this sport-associated, subclinical eating disorder. This concept was modified in 1993 and 1996 by Sundgot-Borgen [49, 50] who added weight loss, restriction of caloric intake and the fear of becoming obese as symptoms. One finds a continuum ranging from relatively minor abnormal eating behaviour such as AA to full-blown clinical ED in athletes. The following sport-specific characteristics of AA have been suggested [48]: first, the reduction in body mass and/or the loss in body fat mass is motivated by performance and not by a concern for appearance. Second, aside from reduced body mass, weight-cycling (repeated weight loss and regain) is also typical of AA. Third, AA vanishes when the athlete retires from his or her athletic career.

Given these considerations, physicians should be aware that the body mass index (BMI) has limited validity for athletes, since athletes may have lower-than-average body weights and/or body fat percentages, regardless of whether they show signs of AA or other ED. Physicians should thus be alert when diagnosing and ED in endurance athletes, athletes who practice sports which are grouped by weight categories or athletes for whom low body weight provides a competitive advantage [45].

Female athlete triad

A condition known as the female athlete triad, characterised by low energy availability, functional hypothalamic amenorrhoea and osteoporosis, is commonly observed among athletes participating in leanness sports [38]. While the prevalence of all three components tends to be rather low and shows a high level of variation (0–16 %), the presence of one or two concurrent components approaches 50–60 % [4]. The main problem is the athlete’s negative energy balance, whether it is purposefully caused or not. This energy deficiency can alter the activity of the hypothalamic pituitary axes and the hormones involved in menstrual function and bone metabolism. This is especially critical for adolescents, who need adequate nutrition and normal hormone functioning during physical development.

Adipositas athletica

While typical ED as well as AA have been researched broadly among athlete populations [10, 48, 51, 52], less focus has been paid to the other end of the bodyweight/size spectrum. Berglund et al. [8] coined the term adipositas athletica to describe the condition among athletes of having higher than “athletic” “normal” fat mass. Examples can be identified in sport disciplines such as sumo wrestling or open-water long-distance swimming. Research is needed to better estimate the devastating health risks associated with enlarged body mass in this population.

In summary, an increased prevalence of ED among elite athletes is well known. However, the diagnosis is less straightforward in this population, and its pitfalls should be considered. The efficiency of preventive programmes has been documented in athletes, and the combined efforts of psychiatrists and sport professionals are needed to improve treatment and prevention of these diseases [9].

Exercise addiction/exercise dependency

The advantages of regular exercise include maintaining fitness, enjoyment and weight control. However, sometimes if it is overdone, it can threaten physical well-being, social relations or it will be continued despite feelings of depression or feelings of guilt. Nevertheless, to determine the boundary where physical activity ends to be beneficial and then begins to impair health is a key challenge. Various attempts have been undertaken to better describe the problem (for further reading: [29]). In the late-70s, the first articles were published on exercise addiction and the possible risks of acquiring exercise addiction for endurance sport athletes [56]. Whiting [56] provided a useful definition: “Exercise” addiction is characterised by dependency on physical activity in one or more of its forms and by withdrawal symptoms if participation is denied. Dependency manifests itself in an excessive dominance of exercise in everyday life, often to the detriment of other facets such as the family, social contacts or work. Withdrawal symptoms include, on the psychological front, feelings of nervousness, guilt, anxiety and lowered self-esteem and, on the physiological front, headaches and physical discomfort”. A similar definition was published by Hausenblas and Giacobbi [21]. Two types were described by Veale [53]: a “primary exercise dependence” arising on its own and a “secondary exercise dependence” occurring in conjunction with a further illness such as an eating disorder. Secondary exercise dependence is far more common than the primary version and is characterised by the use of exercise as a means to accomplish some other objective such as weight loss. Comparable with other types of addiction, compulsive athletes commonly report the following symptoms: (1) feeling euphoria after an intense work-out (runner’s high), (2) the urge to increase the dose of exercise (tolerance), (3) difficulties in performing professional or social activities and (4) when unable to engage in the activity (abstinence) feelings of shifting mood, irritability or anxiety [1].

There is a lack of research on the prevalence of exercise dependence [36]. In a sample of amateur and professional soccer players, Modolo et al. [36] observed a prevalence of 28 % showing negative symptoms of addiction. According to Mónok et al. [37] who assessed the prevalence of exercise addiction on a national representative sample, exercise addiction in the adult general population is rare (0.3–0.5 %). However, some studies reported much higher numbers. Variations are caused by differences in methodology for diagnosing sport addiction, the population studied, sample size, the method of sampling and of course by the variations in disease definition [36]. While the underlying pathology for secondary exercise dependence might be more obvious, many theories have been suggested for the primary version [29]. Assumptions range from the influence of endorphins after exercise (runners high) to motivating reasons for exercise, which themselves are strongly related to personality traits [55].

Various treatment options have been discussed. It is usually not desirable to discontinue exercise completely. A preferable treatment objective is that athlete returns to “healthy” levels of physical activity [16]. The common co-occurring disorders such as ED or food-related problems should be included in the treatment. It is likely that the reduction in exercise will cause a person to resort to increased bulimic or anorexic behaviour in order to maintain low weight levels. Similarly, in a primary psychiatric setting, it is mandatory to observe compensatory exercises when treating ED.

Dementia pugilistica/chronic traumatic encephalopathy (CTE)

Martland [31] first described the “punch drunk” to refer to dementia pugilistica, the condition found in retired boxers. Dementia pugilistica is present in approximately 20 % of retired boxers and is known to be a risk factor for neurodegenerative disorders including Alzheimer disease (AD) and Parkinson disease (PD). In 2004, Iverson et al. [24] showed that amateur athletes with multiple concussions were 7.7 times more likely to demonstrate a major drop in memory performance than athletes with no previous concussion.

Typically, cognitive deterioration is detected more than 10 years after cessation of exposure to repetitive head trauma. The “classical” description of dementia pugilistica, indicates mainly gait, speech and cognitive disturbances, changes of personality and behaviour as well as extrapyramidal symptoms. Recent CTE studies, describing the “modern variant”, point towards the early predominance of neuropsychiatric and behavioural symptoms [27, 32, 33]. Thus, mood disorders (mainly depression), paranoia, agitation and aggression manifest early on, while cognitive impairment, including impairment of orientation, memory, language, attention, information-processing speed and executive functioning, tends to emerge in the later stages [14]. In contrast to the descriptions of “classical” CTE, recent CTE studies have suggested a progression of cognitive symptoms in a somewhat predictable manner [13, 33, 34].

Neuropathological abnormalities of the “classical” and “modern” variants of CTE are roughly similar, as for instance cerebral atrophy, β-amyloid deposition (less prominent in modern CTE), enlarged ventricles and a reduction in pigmentation of the substantia nigra and fenestration of cavum septum pellucidum [33]. However, some important neuropathological differences exist. The accumulation of tau-immunoreactive astrocytes occurs in modern CTE, but not in the “classical” entity [33, 34]. Recent research focuses on the results of microtraumatic brain injuries which are increasingly observed at the end of a professional career despite a lack of clinical correlates found at the time of the injuries. It is assumed that even small asymptomatic brain injuries might lead to CTE [46].

In conclusion, although the relation between trauma and later pathophysiological consequences seems to be straight forward, one should bear in mind that the time interval is rather long and the role of contributing factors such as prevailing genetic risks, alcohol/drug abuse and simple ageing are still under debate.

Mood disorders in the context of overtraining syndrome (OTS)

Burton concluded in his text book of sport psychiatry that athletes experience mood disorders at the same rate as the general population [6]. However, there is still a fair amount of uncertainty with respect to the precise incidence of affective disorders in elite athletes [20, 44]. On the one hand, Resch [43] reported an incidence of depression of 37.5 % among Hungarian elite athletes, and on the other hand, Babiss and Gangwisch [3] suggested that sport participation is a protective factor against depression and suicidal ideation. Nevertheless, most studies assume the same rate in athletes compared with the general population with a comparable gender distribution in favour for women [42]. It has also been shown that retired players with a history of one or two previous concussions were 1.5 times more likely to be diagnosed with depression, while those with a history of three or more previous concussions were found to be three times more likely to be diagnosed with depression [19].

The first important difference between the general population and elite athletes might be the problem of distinguishing OTS from primary depression. Both OTS and depression are characterised by overlapping symptoms such as fatigue, insomnia, appetite change, weight loss, a lack of motivation and concentration difficulties [2]. It is very difficult to disentangle both entities in the acute state. A definite mechanism that triggers OTS is still elusive, despite a long history of research. Initial scientific studies investigated the pathophysiology of heart and lung functioning, skeletal muscles and hormones (e.g. cortisol or catecholamine) as well as the metabolism of carbohydrates, amino acids and lipids [39, 40]. Thereafter, at the end of the last century, brain activity was brought into scientific focus as one causative factor of OTS. Here, research investigated brain blood supply as well as glucose metabolism during physical strain [22, 47]. This was followed by studies on the effect of endurance training on endorphine or neurotransmitter concentrations (e.g. tryptophan and serotonin) which were putatively involved in OT pathology [15, 28, 57]. One theory assumes that the increase in endorphines might lead to addictive behaviour responsible for OTS due to sustained and excessive training. Armstrong and van Heest [2] described clinical and aetiological similarities between depression and OTS. Despite the rather reductionistic idea that changes of serotonin might completely account for symptoms of the OTS, more and more evidence has accumulated during the last years, suggesting an involvement of neurotransmitters and peripheral mechanisms (brain–behaviour–immunity interrelationship) in OTS [35]. This line of reasoning assumes that the brain not only governs simple muscular activity during exercise, but also orchestrates the amount of physical and mental strain by means of complex interactions of biochemical, neuroendocrine and neuroimmunological feedback loops, which is an indication of the physical fitness of a person. This defence mechanism suggests that brain pathology is central to OTS aetiology. Therefore, it was suggested that OTS might be the final attempt of the central nervous system to protect physical health of a subject who exercises excessively. We would like to suggest that research should include psychological factors such as personality traits, personal history as well as social influences to better comprehend the genesis of the OTS.

The treatment regimen for OTC in the context of depressive symptoms can vary enormously dependent on career stage, developmental issues of the athlete, available time resources and predisposing factors. However, the overall combination of psychopharmacology and psychotherapy are of course the methods of choice.

Conclusion

In 1912, the opening lecture of the first German sport physicians convention in Oberhof was given on “Sportübertreibungen” (sport exaggerations) [18]. It took another 100 years before sport-specific psychiatric diseases were brought into scientific focus, and their significance was perceived by a broader community. This change might have been caused by the rise of psychiatric conditions and the considerable increase in emotional stress and professional strains experienced by high-performance and amateur athletes. Elite athletes need to engage in systematic and intensive training from very early onwards to stand the chance of success at the international level. Therefore, they have to leave their families at a very vulnerable age from the developmental point of view. In addition, the increasing media fixation and commercialisation of “success” have led to time-pressure and reduced time for recreation and ultimately has dramatically increased the overall level of emotional stress that people experience in daily life. Thus, we would like to suggest that above-described mental disorders suffered by high-performance athletes are brought about by sport-specific mental stress and that they present to the physician a clinical picture that is specific for this population. Beside the existing research strategies dealing with the amount of exercise, its intensity or the lack of recreation, further research on psycho-soicial factors is needed to better understand the sport specificity of the aetiology of mental disorders in high-performance athletes.

These clinical differences of professional athletes in comparison with the general population are important for establishing the correct diagnosis, for adequate therapy and of course for prevention of mental disorders. Thus, we suggest that the specificity of mental disorders is caused by the interrelation of sport-specific physical and mental demands. In contrast to other demanding professions such as manager or musicians, the athlete has additionally to cope with intense physical strains and related neurobiological and neuroendocrine changes. We believe that this combination of mental and physical demands causes the sport specific clinical presentations of mental disorders. In addition, sport psychiatry is an important subject of education for coaches and other sport-associated professionals such as sport physicians, sport psychologists and physiotherapists. In recent years, some psychiatrists have started to specialise in sport psychiatry to meet the special needs of high-performance athletes. Dan Begel pioneered the field of sport psychiatry and has defined it as the application of psychiatric knowledge and treatment methods to the world of sports [7]. In other words, sport psychiatry and psychotherapy form a discipline whose focus is the investigation, treatment and prevention of the extreme and sport-specific emotional strains and disorders found in athletes [30]. It is the sincere hope of the authors that the investigation of sport-specific strains and disorders will deliver the treatment options and preventive strategies which are so urgently needed to deliver a high-quality service to elite athletes and their specific needs.