[Pain and depression: cognitive and behavioural mediators of a frequent association]

Literature findings: The comorbidity between chronic pain and depression is high: in the general population setting, the odds ratio for suffering from one of these disorders when suffering from the other is estimated around 2.5. For chronic pain patients consulting in pain clinics, the comorbidity rate reaches one third to half of the patients. For the International Association for the Study of Pain (IASP), pain consists in an emotional as well as a sensory dimension, both of them have to be assessed systematically. Likewise, affective disorders must be systematically depicted in chronic pain patients. The reasons for such comorbidity are complex and result from the conjunction of common risk factors (environmental and genetic vulnerability factors) and of a bidirectional causality. THE TRANSACTIONAL MODEL OF STRESS AND COPING OF LAZARUS ET FOLKMAN: The appraisal stress model (Lazarus and Folkman, 1984) offers an opportunity to understand how chronic pain can cause depression. Pain is conceptualized as a chronic stress. Its appraisal in terms of loss, injustice, incomprehensibility or changes (primary appraisal), and in terms of control (secondary evaluation) determine how the subject will cope with pain. Several personality traits as optimism, hardiness or internal locus of control play a protective role on these evaluations, whereas others (neuroticism, negative affectivity or external locus of control) are risk factors for depression. Low perceived social support is also related to depression. On the contrary, self-efficiency is linked with low levels of depression. Self-management therapies focus on increase of perceived control of pain by the patient in order to improve his/her motivation to change, and to let the patient become active in the management of his/her pain.

Conclusion: According to Lazarus and Folkman (1984), coping strategies are the constantly changing cognitive and behavioural efforts to manage specific external and/or internal demands that are appraised as taxing on or exceeding the resources of the person. Pain patients can use a wide variety of pain coping strategies: problem versus emotion focused strategies or cognitive versus behavioural strategies. Some of them are highly dysfunctional, such as catastrophizing (cognitive strategy) or avoidance (behavioural strategy). Their preferential use can lead to the development of a depressive episode. The "fear-avoidance model" (Vlayen, 2000) explains pain chronicization by a vicious circle that begins with the pain catastrophizing; this leads to fear of pain, which in turn leads to avoidance and finally to pain and depression. This is why some behavioural cognitive interventions focus on the reduction of catastrophizing and avoidance. Some functional pain coping strategies were identified: they are active strategies centred on problem resolution such as distraction, reinterpretation or ignorance of pain sensations, acceptance, and exercise and task persistence. New therapeutic interventions focus on the development of better coping strategies such as distraction, relaxation and acceptance.