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, 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 pain, confidence that harm and disability will not occur, and expectations of recovery. Thoughts can negatively influence beliefs about pain 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).

Chronic Pain and Depression

It has been estimated that 35% of the chronic pain population has 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).

In 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. Emerging evidence on the pathogenesis of depression suggests that physiologic similarities exist between depression and chronic pain. Depression and knee pain may also be related to reduced physical activity, which could be due to fear of pain or a consequence of depression (Phyomaung et al., 2014).

Extensive data support the value of tricyclic antidepressants for the alleviation of pain in chronic pain patients, and serotonin and noradrenaline reuptake inhibitors (SNRIs)—duloxetine, venlafaxine, and milnacipran—have shown to be useful 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. The efficacy of duloxetine has also been proven for the treatment of painful diabetic neuropathy (Schneider et al., 2011).

Anxiety and Stress

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).

Stress is the physiologic reaction that occurs in animals and people due to threatened or actual damage to the organism, and can include psychological challenges at the limits of the individual’s coping capacity. Stress-inducing factors are collectively called stressors (Ellegaard & Peterson, 2012).

In the psychotherapeutic treatment of patients with chronic nonspecific low back pain and moderate depression, diverse psychological stressors have been identified, relating to both the past and present. 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).