Studies have shown that pain experienced by the general population is associated with compromised global functioning, as indicated by reduced employment and social activity, negative effects on family functioning, and increased symptoms of depression and anxiety.1,2 However, there is a dearth of research investigating the connection between pain and functioning among individuals with serious mental illness (SMI), despite evidence suggesting that this population has elevated rates of physical health conditions associated with pain, including diabetes and cardiovascular disease.1

Researchers at Boston University in Massachusetts aimed to address this gap in a cross-sectional study published online in June 2020 in Schizophrenia Research.1 They examined associations between clinical pain and global functioning in a sample of 898 participants with schizophrenia or schizoaffective disorder (n=624), bipolar disorder (n=165), or major depressive disorder (MDD; n=109) receiving treatment at 5 centers in the northeastern United States.

Based on responses to the 12-item Short Form Survey, more than one-half of the sample showed some degree of pain interference, with moderate to extreme levels reported by 33% of participants. In alignment with earlier research, pain interference was linked to age and physical health problems. Participants with MDD reported greater pain interference in daily activities in the past month (r=−0.21; P <.05) compared with those with schizophrenia (r=−0.08; P <.05) or bipolar disorder (r=0.02; P =.95 [not significant]). This observation is also consistent with previous findings.

In addition, scores on the Global Assessment Scale revealed that pain interference was associated with lower global functioning after controlling for relevant demographic and clinical variables including physical health conditions.


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These results suggest that patients with serious mental illness should undergo regular screening for the presence of pain. Further research is needed to explore the impact of pain on this population, as well as potential targeted interventions to reduce the effects of pain on functioning. “As pain is a complex and multifaceted experience, specific interventions designed for particular disorders may need to be developed to capture the high rates of heterogeneity found throughout these disorders and SMI more broadly,” the authors concluded.1

Study coauthor Samuel J. Abplanalp, a fifth-year graduate student at the College of Health and Rehabilitation Sciences at Boston University, and W. Michael Hooten, MD, anesthesiologist and psychiatrist at Mayo Clinic in Rochester, Minnesota, who authored a 2016 paper exploring the topic of chronic pain in mental health disorders in detail,3 provided further perspective on the role of pain in mental illness.

What does the evidence thus far suggest about the role of pain in serious mental illness?

Mr Abplanalp: Historically, the role of pain in SMI has been examined using experimental pain induced in laboratory settings. These findings – although somewhat mixed – have led to the conclusion that people with SMI have reduced sensitivity to pain. As a result of this preconceived notion of low pain sensitivity, research into the potential impact of clinical/chronic pain in these populations has been lacking. However, one exception to this is MDD, as myriad research has illuminated the detrimental role that pain may have in this population.

Relatively little work has also been conducted in other SMI diagnoses, particularly schizophrenia and bipolar disorder. This lack of research is concerning given that these diagnoses are associated with clinical pain at rates on par with the general population. In the few studies that have examined pain in schizophrenia and bipolar disorder, results indicate that greater pain is associated with poor outcomes, such as reduced levels of physical activity and increased severity of psychiatric symptoms.

As global functioning is a common construct used in interventions in people with SMI, we wanted to identify the impact of pain on global functioning while accounting for key factors known to influence functioning, such as psychiatric symptom severity. We found that across diagnoses, pain was a significant predictor of poor functioning. Therefore, I think the main takeaway from this finding is that pain is a legitimate problem that could potentially affect numerous facets of life for individuals with SMI.

Dr Hooten: Pain has not necessarily been associated with disorders such as schizophrenia, bipolar I disorder, and MDD with psychosis. Chronic pain has been found to be an independent predictor of depression, and there is also an increased risk of chronic pain syndrome if depression is untreated or inadequately treated (ie, depression is a risk factor for the development of chronic pain).

Certain anxiety disorders may increase this risk, as well. For example, posttraumatic stress disorder (PTSD) has been found to be associated with an increased risk of developing pain.4 Early childhood trauma and stress have also been found to increase the risk of developing chronic pain later in life.5 Such findings show how psychological stress and a stressful environment can predispose an individual to developing pain. The research in this area is very conclusive and really beyond question at this point.

What are some of the mechanisms underlying these associations?

Mr Abplanalp: The mechanisms underlying the associations between clinical pain and functioning in SMI are unclear. Again, not much research has been conducted in this area, and studies on experimental pain have usually focused on group differences between those with and without SMI. We know from depression literature that pain and depression share a reciprocal relationship, such that being in pain can cause depression, and depression can lead to physical symptoms including pain.

There are theories that propose that severity of psychiatric symptoms may lead to greater or reduced pain sensitivity, particularly in individuals with schizophrenia. I am currently working on a study that examines the association between experimentally induced pain sensitivity and negative symptoms in schizophrenia. My goal is that these findings help elucidate some of the underlying mechanisms associated with pain in SMI.

Dr Hooten: Based on the evidence, it can be summarized that certain regions of the brain that process pain signals also process mood, and these shared areas may undergo some sort of neurobiologic shift in response to pain. From a real-life perspective, it will hurt if you stub your toe, but you will also have a negative emotional response to the pain; pain is linked with affect. Imaging studies have shown that the affect component of pain and the nociceptive component are shared.

What are the relevant implications for clinicians in terms of screening and treatment?

Mr Abplanalp: Clinicians are often undertrained in the area of pain and thus are broadly unaware of the detrimental impact pain can have in those with SMI. For example, a patient with schizophrenia who presents with severe delusions and who also reports pain may not have their pain taken seriously as a result of the clinician assuming that pain may be a part of a delusion, or other symptoms – such as delusions and hallucinations – are often a more salient target for treatment. With that being said, I think the main implication for clinicians is simply to recognize pain in these populations. Ideally, pain should be routinely screened for, as identifying its presence could help explain other problems a patient may be experiencing.

Dr Hooten: From a psychological perspective, it is important to recognize that the primary psychiatry population is going to be enriched with patients who have chronic pain, and it is important to screen for chronic pain problems in patients with mental health conditions.

Screening tools such as the Brief Pain Inventory and the Pain, Enjoyment of Life, and General Activity scale are available. However, although these tools can be especially useful for primary care providers, psychiatrists do not need to rely on screeners as much. I advise that they start by simply asking [their patients if they have been experiencing pain].

Clinicians should be diligent in screening for chronic pain and, if it develops, getting patients to the right kind of specialist who can provide a proper diagnosis and evidence-based treatment plan. The first step is to talk to the patient’s primary care specialist and then, if needed, consult with a pain specialist. 

What are some of the ongoing needs in this area in terms of research or education?

Mr Abplanalp: Related to an earlier point, one critical need in terms of research and education centers on clinicians and their ability to accurately identify pain in patients with SMI. Clinicians need to be better educated on pain, and research needs to help clinicians identify potential biases in pain treatment in individuals with SMI. Another area of future research relating to pain in SMI is to identify how pain fluctuates in everyday life. Using methods such as ecological momentary assessment, we can identify how individuals with SMI experience and report pain in real time. This research may lead to ecological momentary interventions, with the goal of intervening in the pain experience in patients’ daily living.

Dr Hooten: There is a need to identify new treatment strategies for chronic pain in individuals with mental health conditions. However, many patients do very well with nonpharmacologic, noninterventional approaches. From a wellbeing perspective, regular exercise, healthy diet, and “good, old fashioned” stress management can improve pain and will also improve many other parameters of health.

References

1. Abplanalp SJ, Mueser KT, Fulford D. The role of physical pain in global functioning of people with serious mental illness. Schizophr Res. Published online June 1, 2020. doi:10.1016/j.schres.2020.03.062

2.     Dueñas M, Ojeda B, Salazar A, Mico JA, Failde I. A review of chronic pain impact on patients, their social environment and the health care system. J Pain Res. 2016;9:457-467. doi:10.2147/JPR.S105892

3.     Hooten WM. Chronic pain and mental health disorders: shared neural mechanisms, epidemiology, and treatment. Mayo Clin Proc. 2016;91(7):955-970. doi:10.1016/j.mayocp.2016.04.029

4.     Ravn SL, Vaegter HB, Cardel T, Andersen TE. The role of posttraumatic stress symptoms on chronic pain outcomes in chronic pain patients referred to rehabilitation. J Pain Res. 2018;11:527-536.

5.     Kascakova N, Furstova J, Hasto J, Madarasova Geckova A, Tavel P. The unholy trinity: childhood trauma, adulthood anxiety, and long-term pain. Int J Environ Res Public Health. 2020;17(2):414.