Gatchel (1991, 1996, 2004, 2005) has proposed a conceptual model of how acute musculoskeletal pain can progress into a chronic pain situation, using a three-stage model (see Fig. 12.1). In stage 1 of this model (referred to as the acute phase), normal emotional reactions, such as fear, anxiety, and worry, develop subsequent to the patient’s perception of pain. This is a natural emotional reaction that often serves a protective function by prompting the worker to heed the pain signal and, if necessary, seek medical attention for it. For example, if workers injure their backs lifting a heavy load, their perception of pain will motivate them to seek medical attention and care. However, if the perception of pain persists beyond a 2- to 4-month period (which is usually considered a normal healing time for most pain syndromes), the pain begins to develop into a more chronic condition, leading to stage 2 of the model. During this stage 2, psychosocial and behavioral problems are frequently exacerbated, such as learned helplessness, anger, distress, and somatization. The extent of these symptoms usually depends on the worker’s preexisting personality and psychosocial structure, in addition to socioeconomic and environmental conditions. For example, depressive symptoms will be greatly exacerbated during this stage for the worker if he/she has a premorbid depressive personality and is seriously affected economically by loss or absence of a job due to the pain and disability. In a similar fashion, if the worker had premorbid hypochondriacal characteristics and then also receives a great deal of secondary gain (e.g., sympathy from others), he/she will most likely display a great deal of somatization and symptom magnification, as well as being disabled from the workplace. In essence, this conceptual model takes a diathesis-stress perspective, in which the stress of coping with pain and disability can lead to exacerbation of the worker’s underlying psychosocial characteristics (diathesis). However, this model does not propose that there is a preexisting pain-prone personality. Rather, it proposes that patients “bring with them” certain predisposing personality and psychosocial characteristics (i.e., they have a diathesis) that is then exacerbated by the stress of attempting to cope with the now chronic nature of the pain and disability. Such a relationship between stress and the exacerbation of mental health problems has been well documented in the scientific literature (Gatchel, 2005). It should be clearly noted that this is not to say that predisposing factors make chronic pain a psychogenic disorder and that it is “all in the patient’s head.” Rather, the chronic pain and disability problems represent a complex interaction among physical, psychosocial, and economic variables.

In the past, this diathesis-stress perspective had also been applied to the development of musculoskeletal pain by other investigators (e.g., Flor & Turk, 1984; Turk & Flor, 1984). According to this perspective, chronic pain and disability disorders are a function of the interaction between a patient’s premorbid biological and psychosocial predispositions (diatheses) and the stressors or challenges (stress) that occur as the result of some physical injury/impairment and possible tissue damage (Banks & Kerns, 1996). Thus, for example, patients who may have some premorbid diathesis will have a greater risk of developing pain and/or disability as a result of an occupational injury, relative to those who do not have such a diathesis (Flor & Turk, 1984; Turk & Salovey, 1984). These authors go on to give the example of low-back pain, which may occur if the patient has a diathesis or predisposition to develop hyperactive back muscles, as well as having poor coping skills and work-related stress. These underlying predispositions can be either genetic or early-learning experiences. Turk and Salovey (1984) also highlighted the fact that once stress and accompanying physiological activations stimulate these factors, then a pain cycle can begin. The pain, now acting as a new stressor, will then further increase muscle tension and tax-coping skills; this pain cycle then is further perpetuated.

Finally, the progression to more complex interactions among physical, psychological, and social processes characterizes stage 3, which represents the chronic phase of this model. As the result of the chronic nature of the pain experienced, and the stress, disability, and impairment that it may create, the patient’s life now begins to revolve around the pain behaviors that maintain it. The patient may begin to adopt a “sick role,” in which any excuse from social and occupational responsibilities become routine. As a result, the patient now becomes accustomed to the avoidance of responsibility and other reinforcers that maintain such maladaptive behavior, as well as his/her disability. For example, the hypothetical pain patient from above not only stops working or trying to maintain a job but he/she may also avoid other activities, such as walking in the park with a spouse or engaging in leisure-time activities like going to the movies, shopping, etc. At the same time, while receiving disability payments, he/she gets to sit at home watching the television all day, and family members and friends may run errands for him/her, thereby facilitating the disability.

In addition, superimposed on these three stages is what is referred to as the physical deconditioning syndrome, which was originally described in detail by Mayer and Gatchel (1988). This is a significant decrease in physical activity (such as strength, mobility, and endurance) because of the pain and disability that result from disuse and produce atrophy of the injured area. There is usually a two-way pathway between the physical deconditioning and the three stages described above. For example, physical deconditioning can feedback and negatively affect the emotional well-being and self-esteem of workers. This can lead to further negative psychosocial sequelae. Conversely, negative emotional reactions, such as depression, can feedback into physical functioning (e.g., by decreasing the motivation to get involved in work or recreational activities and thereby contributing further to physical deconditioning). Overall, this creates a vicious cycle between physical conditioning/disability and psychosocial/psychiatric issues. Of course, the important key in treating occupational pain is not let it to progress into stages 2 and 3 levels where more complex biopsychosocial interactions and problems develop. Early intervention for acute occupational pain problems is now the recommended treatment option (Gatchel, 2005).

There can be no doubt that as the vicious pain cycle (based on the earlier reviewed diathesis-stress model) becomes more chronic in nature, psychosocial/psychiatric variables begin to play an increasingly dominant role on the maintenance of pain and disability behavior and suffering (Gatchel, 2005). A major issue raised in the past has been the “chicken-or-egg” question: are the psychosocial/psychiatric problems secondary to the chronic pain, or are these problems the primary syndromes of which chronic pain is merely a symptom? In one of the first studies to evaluate this “chicken-or-egg” question, Polatin et al. (1993) evaluated 200 chronic occupational low-back pain patients for current and lifetime psychiatric syndromes (using a formal structured interview method for determining official Diagnostic and Statistical Manual Disorders) diagnoses. Their diagnostic results revealed that even when the controversial category of somatic pain disorder was excluded, 77 % of patients met lifetime diagnostic criteria, and 59 % had current symptoms for at least one psychiatric diagnosis. The most common psychiatric diagnoses were major depression, substance abuse, and anxiety disorders. Moreover, 51 % met criteria for at least one personality disorder. All of these prevalence rates were significantly greater than the base rates in the general population. Moreover, one of the most important findings of this study was that of those patients with a positive lifetime history for psychiatric syndromes, 54 % of those with depression, 94 % of those with substance abuse, and 95 % of those with anxiety disorders had experienced these syndromes before the onset of their chronic low-back pain. These were the first systematic results to objectively document that certain psychiatric syndromes appear to precede chronic low-back pain (substance abuse and anxiety disorders), whereas others (specifically, major depression) can develop either before or after the onset of chronic low-back pain.