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PSYCHOGENIC PAIN: Perceptions, emotions and attitudes

When psychological factors are judged to be a major factor and pain is the main focus of the patient’s attention, resulting in significant distress and social and occupational dysfunction, it is described as a Pain Disorder in the system of classification generally preferred by courts (the current, 4th edition of the Diagnostic and Statistical Manual of Mental Disorders [DSM; published by the American Psychiatric Association, Washington DC, USA, in 1995], coded as F45.4). This pain of psychological origin — or psychogenic pain — is difficult to treat, and occurs surprisingly often. The exact incidence of psychogenic pain disorders is unknown, but in the USA, psychogenic back pain alone causes some form of work disability in an estimated 10–15% of adults every year (DSM–IV). When numerous, often dramatic, physical symptoms — including pain — typically affecting several organ systems, are present, psychogenic pain is diagnosed as a somatization disorder. When there is a pathological preoccupation with minor symptoms, hypochondriasis is diagnosed. In all of these conditions, sufferers are troubled by introspections — the changes in their lives, the alarming prospect of indefinite future pain and the threat to comfort and aspirations. Denial of psychological factors is common. A ‘somatic presentation’, where patients ‘presented only physical symptoms to their doctor, and attributed neither the aetiology nor any exacerbation of these symptoms to psychological factors’ was observed in 25% of attenders at General Practitioners’ surgeries. Pain thresholds vary — not only between individuals but also in the same individual depending on circumstances, expectation, attention, arousal and emotion. Involuntary preoccupations are the core of many disorders, including obsessional compulsive disorder, anorexia nervosa and body dysmorphobic disorder. Preoccupation with pain and with the future implications will increase the severity. One can be distracted momentarily from a nagging pain such as a toothache by something interesting and engaging; by the same token, pain is increased when one is tense, anxious or depressed. In the heat of a match, sportsmen may be largely oblivious to injury. In contrast, the term ‘tension headache’ illustrates a situation where there is pain as a result of psychological factors. The subjective experience of pain is accompanied by neurochemical changes, as illustrated by the effect of placebos, which can be blocked by giving naloxone. Naloxone antagonises the body’s own opiate-like substances, endorphins. The fact that the beneficial effects can be neutralized in this way indicates that placebos induce discernable chemical changes in the body’s response which explain their analgesic effects. Neural pathways have been traced that link pain receptors and pathways to brain structures which modulate emotion and cognition, which in turn establishes response priorities. The mechanisms are complicated. As well as nerve impulses travelling up to the brain, they travel down from the brain (the cortio-fugal pathways), adjusting and focusing the sensitivity of the sense receptors. For example, a hungry man is sensitized to the sight and smell of food; and the activity in the nerve relay terminal from the ear (cochlear nucleus) is decreased in cats when they are looking at mice or exposed to fish smells. Once pain starts, and particularly if it is prolonged, central adjustments to pain thresholds in a deep-seated brain structure (the thalamus) may occur, which change the perceived quality of the train of neural impulses and their interpretation. This central adjustment makes the experience peculiarly unpleasant. This mechanism is involved in phantom-limb pain in an amputated limb, which illustrates the reality of the pain experience when the original source has ceased to exist.