Pain perception—the conscious recognition and awareness of a painful stimulus—is modulated and modified by many psychological and personality-related factors. These can include previous pain experiences, emotions and cognition, somatization and catastrophizing, the presence of acute and chronic stressful life events, fatigue, anxiety, fear, boredom, and anticipation of more pain. Pain perception is also influenced by socioeconomic factors such as social support, acceptance, incentives, education, occupation, and quality of life. In addition, pain perception differs among genders and ethnicities, and varies with age (Belfer, 2013).
Chronic pain in particular carries with it personal and economic costs and psychological distress, and psychological factors play a significant role in chronic pain. Pre-existing depression, anxiety, and stress may predispose some individuals to progress to a chronic pain condition, while chronic pain in turn leads to anxiety and depression, creating a vicious cycle (Rice et al., 2016).
Because of the cognitive, emotional, and psychological effects that may be associated with pain, a biopsychosocial concept of pain has emerged over the past two to three decades, along with considerable evidence supporting management approaches that address the psychosocial aspects of a patient with chronic pain (Sessle, 2012).
Within the biopsychosocial model, research on beliefs shows that negative pain beliefs have a detrimental impact on patients’ overall health, self-efficacy, and function. Thoughts can positively influence beliefs about the pain experience if there is control in managing the pain, confidence that potential harm and possible disability are not threatened, and there are expectations of recovery. Thoughts can negatively influence beliefs about the pain experience if control is lacking and recovery is not possible. The consequence can be emotional distress and catastrophizing, as well as excessively negative and pessimistic beliefs and thoughts about pain (Pons et al., 2012).
Beliefs that contribute to poor compliance, motivation, and misunderstanding about pain include catastrophizing, limited control over the pain, and emotional distress. Catastrophizing is associated with persistent pain and it is a predictor of poor outcomes in pain interventions. Although catastrophizing and emotional distress have common characteristics, it is difficult to separate their overall effect (Pons et al., 2012).
Chronic Pain and Depression
It has been estimated that 35% of the chronic pain population has comorbid (associated) depression (Bromley Milton et al., 2013). Pain can be a symptom, a cause, or a consequence of depression. Studies investigating the association between pain and depression suggest that the stress of living with chronic pain can cause depression, but there is also evidence that pain develops secondary to depression, manifesting as increased pain sensitivity, and that high depression scores are associated with greater risk of developing chronic pain (Schneider et al., 2011). The association between depression and pain appears to increase with the severity of each condition (Bromley Milton et al., 2013).
Failure to treat pain in depressed patients may adversely impact depression treatment outcomes. Recognizing and optimizing the management of pain may be important in enhancing depression remission rates. The presence of severe pain at the start of depression treatment has been seen in those who failed to respond to antidepressants, and a lower overall pain severity score at the outset was associated with higher odds of achieving remission (Schneider et al., 2011).
In a systematic review of studies looking at the psychological factors associated with knee pain, researchers found strong evidence for a positive association between depression and knee pain in adults. The emerging evidence on pathogenesis of depression suggests that it is associated with dysfunction in the inflammatory cytokine production as a response to stressors, dysregulation of the autonomic nervous system, and destabilizing effect on hypothalamic-pituitary-adrenal axis. Each of these mechanisms also contributes to the development of chronic pain syndrome. These findings indicate that physiologic similarities exist between depression and chronic pain (Phyomaung et al., 2014).
Another explanation for the association between depression and knee pain may be reduced physical activity, which could be due to fear of pain or as a consequence of depression. The muscle wasting and reduced joint stability resulting from low activity may have a negative effect on function and the disease outcomes of osteoarthritis (Phyomaung et al., 2014).
Extensive data support the value of tricyclic antidepressants for the alleviation of pain in chronic pain patients, and the newer serotonin and noradrenaline reuptake inhibitors (SNRIs)—duloxetine, venlafaxine, and milnacipran—have shown to be usseful in the treatment of pain and depression. Duloxetine is a SNRI with proven efficacy for painful physical symptoms of depression. Analyses from short-term trials demonstrated that a greater reduction in pain was associated with a higher probability of remission. Furthermore, the efficacy of duloxetine has been proven for the treatment of painful diabetic neuropathy (Schneider et al., 2011).
Chronic Pain and Anxiety
Anxiety is common in chronic pain patients and anxious patients may interpret pain as being more intense than non-anxious patients. The presence of chronic pain makes it difficult to recognize and treat potential psychiatric disorders, and this delay may worsen the prognosis of psychiatric disorders (Mangerud et al., 2013).
In a cross-sectional study of Norwegian adolescents with psychiatric disorders, two-thirds reported chronic pain. Adolescents with mood or anxiety disorders had a significantly higher frequency of chronic pain and pain-related disability than those with hyperkinetic disorders. Adolescents with hyperkinetic and mood or anxiety disorders had a two- to three-fold increased risk of pain-related disability compared to those with hyperkinetic disorders alone (Mangerud et al., 2013).
Research has shown a link between low back pain and psychological factors, particularly depression and anxiety. In relation to low back pain, depression is often described as being atypical and takes the form of a so-called masked depression, often following a traumatic event. Individual psychological intervention is recommended as the primary treatment, with medical treatment secondary (Ellegaard & Peterson, 2012).
Stress
Stress is the physiologic reaction that occurs in animals and people due to threatened or actual damage to the organism, including psychological challenges at the limits of the individual’s coping capacity. Stress-inducing factors are collectively called stressors (Ellegaard & Peterson, 2012).
A study showed that in psychotherapeutic treatment of patients with chronic nonspecific low back pain and moderate depression, diverse psychological stressors were identified, relating to both the past and present. The study found that when pain, stress, and depression become overwhelming and there are few resources available, stress seems to become prominent. Stressful situations can lower a person’s ability to cope with back pain (Ellegaard & Peterson, 2012).