Behind the Book

We asked lead editor Emeran A. Mayer, MD, what makes the book an important landmark in the pain field.
 
Q: What are functional pain syndromes?
A: Functional pain syndromes, including such common disorders as irritable bowel syndrome (IBS), fibromyalgia (FM), temporomandibular joint disorder (TMJD), and interstitial cystitis (IC), are chronic symptom-based syndromes that affect up to 15% of the population worldwide. They are characterized by chronic pain and discomfort referred to different regions of the body. Traditionally, most patients visit general practitioners, who refer some of them to various medical and surgical subspecialities, depending on the predominant symptoms. No generally agreed-upon structural, inflammatory, or biochemical abnormalities have been identified that could fully explain the symptoms. Patients show a greatly reduced quality of life, yet treatment options are limited, and the development of novel therapeutic approaches has been disappointing.
 
Q: Is there any overlap among the functional pain syndromes?
A: Specialists tend to develop symptom-based criteria for each syndrome without considering the frequent overlap of these syndromes with one another and with psychiatric syndromes, such as anxiety, depression, and somatization. Only recently have clinicians and investigators begun to focus on the shared features of these syndromes. This book brings together experts from the fields of pain medicine, gastroenterology, psychiatry, physiology, genetics, and neuroscience who review the growing evidence that these disorders have substantial comorbidity with each other.
 
Q: Are these disorders considered “psychosomatic” in origin?
A: The term psychosomatic has traditionally been associated with a conceptualization of physical disease as a manifestation of psychological processes and conflicts. Thus, this term does not reflect the current view that these syndromes are based on an altered bidirectional interaction between the nervous system and the body. Central pain amplification and altered autonomic nervous system activity are two of the mechanisms most commonly implicated in generating symptoms. Nevertheless, experts have come to recognize psychological factors—chronic stress and symptom-related worry in particular—as important factors in symptom onset and severity.
 
Q: Why are functional disorders more prevalent in women?
A: Although it could be said that women in general are more likely to consult a health care provider when they have symptoms of illness, there is good evidence that these syndromes really are more common in women. Preliminary evidence suggests that sex-related differences in emotional arousal circuits and in endogenous pain modulation systems may play a role in the greater vulnerability of women. In addition, we have an incomplete understanding of the role of sex hormones.
 
Q: Do these disorders have any pathophysiological aspects in common?
A: The traditional, subspecialty-focused view of these disorders has emphasized the differences and ignored the shared features. This book represents a new perspective that has begun to emerge in the past five years. The occurrence of different functional disorders in the same patient (either at the same time or at another point during his or her lifetime), the comorbidity with certain psychiatric disorders, shared risk factors (early life trauma and gene polymorphisms), the sensitivity of symptoms to stress, and a good response to centrally targeted therapies (cognitive-behavioral therapy or low-dose tricyclic antidepressants) all point toward shared pathophysiological mechanisms.
 
Q: How do anxiety and depression relate to functional pain disorders?
A: Numerous epidemiological studies have demonstrated a high prevalence of psychiatric diagnoses (most commonly, anxiety and depression) in patients with these syndromes. Increased levels of depression, anxiety, and somatization (a high number of somatic complaints) are typical in most patients. Certain syndromes, such as IBS, tend to show comorbidity with anxiety, while others, such as FM, show a greater comorbidity with depression.
 
Q: Is there any evidence of a genetic predisposition to functional pain disorders?
A: Considerable evidence from twin studies, and more recently from studies of gene polymorphisms, indicates a genetic predisposition to develop these syndromes. Some of the best data come from prospective studies of the development of TMJD. Several obstacles stand in the way of our understanding of the role of heritability in functional disorders. First, these syndromes are likely to be polygenic disorders, where the contribution of each gene to the clinical phenotype may be less than 5%. Second, studies have been limited by the subspecialty-based definitions of different syndromes. A shared genetic predisposition for all these syndromes may manifest as IBS in one family member and as FM or TMJD in another, and this variable manifestation may be due to different environmental factors. Thus, the role of genetic factors and heritability may be significantly higher than is currently suggested.
 
Q: Does the book provide any new insights on post-traumatic stress disorder?
A: There is considerable comorbidity of many of the functional pain disorders with PTSD. Brain-imaging studies of patients with PTSD and functional pain disorders have demonstrated certain shared abnormalities in brain circuits, including a reduced ability to activate corticolimbic inhibition pathways. There may also be shared genetic and early-life vulnerability factors in PTSD and functional pain syndromes. The book explores these issues in the chapter on combat-related psychiatric syndromes.
 
Q: Does the book include treatment recommendations?
A: Most of the chapters on individual syndromes contain information about current therapies. In addition, specific chapters discuss the details of pharmacological, cognitive behavioral, and complementary and alternative therapies.
 
Q: Is there any overlap among the treatment options for these disorders?
A: There is considerable overlap among treatment options, particularly with centrally targeted therapies. Anxiolytics, low-dose tricyclic antidepressants, selective serotonin reuptake inhibitors, nonselective reuptake inhibitors, and nonpharmacological approaches (such as cognitive-behavioral therapy) all show benefit in subgroups of patients in different diagnostic categories.
 
Q: Are nonpharmacological approaches effective?
A: The best evidence for the effectiveness of such therapies comes from controlled trials into cognitive-behavioral therapy and hypnosis. An emerging view is that different subgroups of patients may benefit the most from pharmacological or nonpharmacological therapies (including cognitive-behavioral and complementary medicine approaches). A combination of these approaches may be synergistic.