The Missing “P” in Psychiatric Training: Why is it Important to Teach Pain to Psychiatrists?

Introduction

Chronic pain is a public health problem of pandemic proportions that afflicts over 70 million Americans ^{1, 2} and remains the most common complaint brought to the attention of health care practitioners ³. Its annual cost to the American society is staggering and is estimated to be around $100 billion owing to medical costs and loss of earnings and productivity ⁴. The current demographic trends ⁵ and the tremendous shortage of pain experts ⁶ forecast the need for even greater attention to pain from the medical establishment in consequence of the substantial rise in the overall proportion of geriatric population that is naturally at a heightened risk for the development of pain-related conditions ⁷. Specifically, 50% of community-dwelling elders and up to 80% of nursing home residents are afflicted with chronic pain ⁸. The rates of Americans over the age of 65 has increased steadily due to the rise in life expectancy and decline in fertility from 4% at the beginning of the 20th century to 12% nowadays with projected over 20% (70 million) over the next 25 years ⁹. Pain is exceedingly prevalent in psychiatric samples ¹⁰ and since more people will be suffering from pain so will psychiatric patients ¹¹.

One of the most daunting challenges faced by psychiatric practitioners is how to distinguish and approach physical and emotional symptoms arising in the context of pain experienced by their patients. We respond to this question by proposing to integrate fundamental tenets of pain medicine within the core psychiatric residency training curriculum ¹². Besides altered pain function ^{13, 14}, psychiatric patients can be noncompliant with pain treatment and additionally develop co-morbid addiction to opiate analgesics ¹⁵. On the other hand, chronic pain is frequently associated with anxiety and depressive symptoms ¹⁶ as well as with degenerative cortical changes that may further deteriorate affective states and cognition ^{17, 18}.

Sensory areas are recruted by both acute and chronic pain, but the latter is a more complex phenomenon engaging a broader stress-related neural network with emotional, motivational and cognitive components ¹⁹ that converge on circuits such as the mesocorticolimbic dopaminergic and endogenous opioid, involved in salience/reward/motivational mechanisms in addition to responses to pain, more generally stressors and their regulation ²⁰. With this premise of neurobiological overlap between the processing of pain and of other stressful and emotionally salient signals, the present paper considers the aspects of pain that are related to stress, reward and motivational regulation and are pertinent to psychiatric morbidity. First, we compare data on the neural mechanisms that underlie physical and emotional types of “pain”, and this comparison is taken as the basis for the assumption of overlap between these frequently related entities. Second, we summarize the mechanisms involved in the mediation of pain and analgesia, as they relate to normal processing of emotions, reward and motivation as well as their alterations encountered in psychiatric patients. The same section also covers specific background demonstrating that pain-related stimuli provide a reliable functional probe of the brain reward/salience/motivation circuitry and may thus have heuristic value for the inquiry into neurobiology of psychiatric illnesses. Next we provide specific clinical context on the association between psychiatric disorders and pain conditions. Finally, the two last sections cover psychiatrists’ training in pain medicine and the importance of this endeavor.

Physical and Emotional Pain may Represent Two sides of the Same Coin

In addition to the epidemiological association between pain and psychiatric disorders ¹⁰, there are clinical, even diagnostic features of pain syndromes that point to neuropsychiatric origin. Pain’s definition by the International Association for the Study of Pain (IASP) as "an unpleasant sensory and emotional experience associated with actual or potential tissue damage" ²¹, recognizes its multifaceted bio-psycho-social nature with causes that extend well beyond direct physical harm. This is expressed in the Diagnostic and Statistical Manual of Mental Disorders, fourth edition, text revision (DSM-IV-TR) as the Axis I diagnostic category of the Pain Disorder, which is encoded in three of the five diagnostic criteria, viz., A. Pain…is of sufficient severity to warrant clinical attention; B. Pain causes clinically significant distress or impairment in social, occupational, or other important areas of functioning; C. Psychological factors are judged to have an important role in the onset, severity, exacerbation or maintenance of pain ²². Pain arising from physical sources is classified among the DSM-IV-TR Axis III disorders, solely reserved for medical conditions ²². In the reality the distinction between Axis I and III Pain Disorders is not that obvious and both pain categories share clinical characteristics, symptom severity and functional impairment ²³. Realization of such blurring of diagnostic boundaries is rooted in the lay language where the “pain” term is used interchangeably in both physical and emotional contexts ²⁴.

Pain and the Brain: Implications for Emotional and Motivational Processing

Acute pain signals real or perceived tissue damage from environmental threats ²⁵. Contextually, albeit not clinically similar, cancer pain is also etiologically linked to direct tissue damages due to malignancy or to surgical, chemotherapy or radiotherapy treatments ^{26, 27}. Chronic non-malignant pain is not a unitary sensation evoked by a local injury, inflammation or other tissue pathology but is a complex state modulated by genetic, environmental, cognitive and emotional factors ^{28, 29}. Majority of non-malignant chronic pain cases are neuropathic viz., caused by alterations in the central nervous system ¹⁹. Such centralization is conceptualized as an independent neuropsychopathological disease state, occurring at the level of the spinal cord pathways and emotional/motivational circuits, respectively manifested in exaggerated response to painful (hyperalgesia) and non-painful (allodynia) stimuli in combination with negative affective states and persistent drive to eliminate pain via behavioral or pharmacological measures ^{19, 30, 31}. The apparent intricate link between pain and emotions/motivations underscores the importance of dynamic interactions between these and other (e.g., neurochemical and neuroanatomical) factors for understanding of health and psychopathology (Figure 1).

Figure 2 schematically displays a somewhat representative compilation of the interactions between sensory and emotional systems with ensuing affective states and symptomatology. Evidence of such interaction is provided by functional magnetic resonance imaging (fMRI) work showing that grief-related emotional pain activates classical physical pain circuitry (e.g., periaqueductal gray, insula and the anterior cingulate cortex) ³² while physical pain in humans activates reward/motivational circuits (e.g., nucleus accumbens [NAc] and ventral tegmentum [VT]) ^33–35. Furthermore, acute emotional or physical pain in patients with the respective chronic conditions (i.e., complicated grief and back pain) via exposure to reminders of the deceased³² or thermal pain ³⁶ robustly engages the key reward and reinforcement structure, namely the NAc. These finding suggest that emotional and physical pain may become a reinforced stimulus in some conditions (e.g., complicated grief and chronic back pain) thus providing partial explanations for their unremitting course. In a broader sense, critical for the survival mechanisms pain system, is embedded within extensive emotion/reward/motivation circuitry, representing a neural network responsible for continued existence of individuals and species via pursuit of food, water, and sex as well as via learning, decision making and adaptation to stress. Considering survival significance of social affiliations, their pleasurable acquisitions and painful losses may have evolutionarily tapped the same reward systems ³⁷; an idea consistent with the reward-pain continuum hypothesis promulgated by Baruch Spinoza. A practical offshoot of the reward-aversion continuum is that pain serves as a functional probe of the brain reward and motivational systems ³³. This is an important contribution, given the paucity of reliable probes and the pivotal role played by reward and motivation in the course of psychiatric illnesses.

Co-morbidity of Pain and Psychiatric Disorders

Provided that the emotional brain circuitry abnormalities are arising in psychiatrically healthy people exposed chronic pain ¹⁸, a compelling a fortiori argument is that propensity for pain condition is worsened by neuropsychopathology affecting the same neural structures. A model partially suited to explain this link is the diathesis-stress theory postulating preexisting sometimes subclinical traits that manifest in the form of overt psychopathology in the context of prolong pain-induced stress ^{16, 38,39}.

The list of psychiatric ailments associated with heightened pain prevalence in at least one extant epidemiological survey would stretch the entire DSM-IV-TR diagnostic range from the Disorders Usually First Diagnosed in Infancy, Childhood or Adolescence to Other Conditions that may be a Focus of Clinical Attention. For the purpose of the present discussion we address four common and representative syndromes, namely, the major depressive disorder (MDD), borderline personality disorder (BPD), addiction and post-traumatic stress disorder (PTSD).

Pain Training in Psychiatry

Pain themes are only marginally addressed by the respective training and certification requirements set forth by the Accreditation Council for Graduate Medical Education (ACGME) ¹⁵⁹ and the American Board of Psychiatry and Neurology ¹⁵⁹. The former includes Intractable Pain among Medical Knowledge items but not among Patient Care competencies, while the latter only lists Pain Medicine in the section on Psychiatric Subspecialties and Other Areas of Psychiatric Endeavors. Psychiatrists appear to be inadequately trained in pain medicine and to consequently perceive their work with pain patients as ungratifying ^{160, 161} so the present psychiatric training requirements may be suboptimal for the physicians that are uniquely poised to evaluate and treat pain patients whilst sharing responsibility with their medical colleagues for the management of mental health issues ¹⁶².

Empirical data on potential benefits of increased pain training for psychiatric residents are missing. This line of inquiry may be limited by educators’ concerns that any training add-ons may encroach on the time honored intensive and rigorous curriculum of the critical clinical skills and knowledge base ¹⁶⁰. In our opinion, far from being adverse for psychiatric education, participation in pain training may be beneficial for psychiatric residents, their patients and medical field as whole.

Pain curriculum could build upon the residents’ proficiency in neurobiology and upon the existing IASP guidelines ¹⁶³. Since there are countless ways in how the training can be operationalized, a consensus concerning the adoption of various training components perhaps needs to be developed by a Committee comprised of Psychiatric Residency Training Directors and/or through the American Psychiatric Association Task Force. Following is a brief outline of possible components that may be included in the training activities.

The main objective of the first post-graduate year (PGY-1) is to shape the physician identity of new medical school graduates. Recent graduates accordingly spend at least four months in primary care clinical settings and so that part of their caseload requirements may include treatment and follow up of chronic pain patient(s). This clinical experience can be reinforced via didactics and direct patient care during the two months mandatory neurology rotation. The PGY-2, focused on the foundations of physicians’ identities as psychiatrists may include assessments of dually diagnosed pain/psychiatric patients in conjunction with psychotherapeutic ¹⁶⁴ and psychopharmacological ⁴⁹ strategies in the treatment of pain patients. The PGY-3 provides an opportunity to refine the previously acquired skills in more specialized settings including inpatient detoxification unit and outpatient addiction clinic. Consultation-liaison rotation in the PGY-4 could emphasize the integrative nature of pain treatment within the context of medicine at large and the distinctive role of psychiatrists in identifying and handing individual and interpersonal issues within the medical team arising in the context of challenges inherent in the care for multi-problem and at times non compliant and treatment resistant pain patients.

Why is it Important to Teach Pain to Psychiatrists?

Rather than viewing psychosocial and biological interventions as distinct therapeutic modalities, psychiatrists are exceptionally trained to conceptualize patients’ care on the psychosocial-biological continuum and to shift flexibly across various parts of this spectrum among patients and treatment junctions. Thus, wide-ranging involvement of psychiatrists will invigorate essential elements of evaluation and treatment armamentarium that may be underutilized by their medical colleagues. This is a timely effort because majority of neuropathic pain is only partially responsive to opioids ^{27, 165} so innovative approaches are essential for the pain field.

Psychiatrists are understandably suited to recognize and manage subtle psychological processes including expression of feelings via somatic pain complaints ¹⁶⁶, defense mechanisms e.g., denial and repression vs. lie and malingering along with conscious and unconscious motivations ¹⁶⁷ such as self reported pain in the face of adequate analgesia due to unwarranted anxiety about the opioid dose reduction (i.e., pseudo-opioid resistance; ¹⁶⁸) or drug craving vs. pseudo-addiction ⁸⁴ or therapeutic dependence ⁸⁵. Additional pertinent function is the motivational enhancement ¹⁶⁹ fostering compliance and active participation in pain treatment plans ⁸⁰.

While multiple cognitive and behavioral strategies (e.g., cognitive restructuring, stress management and systemic desensitization) were reportedly helpful for chronic pain ^{164, 170}, National Institute of Health Technology Panel assigned the highest score (i.e., strong) to the evidence regarding the effectiveness muscle relaxation ¹⁷¹. Psychiatrists can become strong advocates for the utilization of cognitive and behavioral techniques by the pain field as they routinely apply them to the care of psychiatric patients. Moreover, being undisputed experts in psychopharmacology, psychiatrists can promulgate viable and non-addictive alternatives to opioids with substantial analgesic properties such as antidepressant, anticonvulsant and neuroleptic agents (⁴⁹, however see ¹⁷² suggesting only minor pain effect of neuroleptics). Also, psychiatrists are the most logical physicians to diagnose and treat suicidal tendencies ^{1, 173} as well as mood, anxiety, psychotic and personality disorders exerting pivotal impacts on pain intensity and treatment outcomes ¹⁶.

The psychiatrists’ dialectical perspective ¹⁷⁴ on pain alleviation while preventing, diagnosing and treating addiction to prescription opioid pain killers is addressed in the preceding sections. Additional contribution from the addiction psychiatry field may involve empirically driven treatment matching algorithms allowing provision of individualized level care according to patients needs with regard to their medical status, employment/support, drug addiction, family situation and psychiatric condition. Patient Placement Criteria by American Society of Addiction Medicine ¹⁷⁵, may be adapted to pain patients ^{176, 177} since they provide multidimensional assessment of severity of illness and level of function and treatment assignment based on needs for service and level of care determination within the available treatment options.

Hence, outweighing any personal benefits for psychiatric trainees per se, this may be of a broader public health interest to engage psychiatrists in the care for the pain patients. Such an addendum will not only generate additional clinical expertise to evaluate and treat a large spectrum of pain-related problems, but will also help expanding the spectrum of psychiatric field to include pain as an entity rooted in numerous other specialties (to name a few: neurology, medicine, surgery and anesthesiology) and will thus advance the integration psychiatry into the mainstream medical care ¹⁷⁸ and underscore the significance of attending in concert to mental and physical problems notwithstanding physicians’ specialties and patients’ presenting problems.

Conclusions

Chronic pain is a major problem afflicting the modern world. The coalescence of epidemiological and clinical data suggests that psychiatric patients have a predilection for a development of various pain conditions. This is at least partially due to functionally impaired neural substrates that overlap emotion, reward, motivation and pain processing. Although psychiatry is only one of many appropriate settings were pain patients can be treated, this approach has several advantages. First, psychiatry is comprehensively focused on the etiopathophysiological mind-body interactions with direct relevance to the pain syndromes. Second, neurobiological research in animal models and more recently in humans confirms a substantial degree of overlap between pain regions and brain areas implicated in core psychiatric symptoms. Third, the relationship and co-morbidity between persistent pain and psychiatric disorders has been extensively documented.

If the interactions between pain and psychiatric illnesses can be further elucidated, they might be used to screen patients at risk for the development or worsening of psychopathology (i.e., primary prevention). It may be also discovered that psychiatric patients need to be targeted for early intervention even in the presence of mild pain problems (i.e., secondary prevention). Lastly, pain medicine training could speed the introduction of other essential ‘medical’ topics to psychiatric curriculum that have now become timely (e.g., metabolic disturbances ¹⁴). Filling in the missing “P” in elevating the psychiatrists’ new role in pain patient care, teaching and research may be a substantial clinical contribution in a domain that currently offers relatively little in terms of adequate therapeutic responses.