Pain is not transmitted from the body to the brain like a message travelling down a wire. Pain is constructed by the brain as an output based on a threat assessment. The brain integrates sensory input from damaged or potentially damaged tissue with contextual information including beliefs, expectations, attention, prior experience, and emotional state, and produces pain as a protective signal. This is why the same injury produces dramatically different levels of pain in different people, and why the same person experiences the same physical condition as more or less painful on different days depending on their psychological state.
Central Sensitisation
Central sensitisation is a well-characterised neurological phenomenon in which the central nervous system, including the spinal cord and brain, becomes more sensitive to pain signals over time. With chronic pain, the threshold for activating pain pathways falls: stimuli that would not normally produce pain begin to do so, and normally painful stimuli produce exaggerated responses. This amplification is not imaginary. It is a real neurological change produced by sustained nociceptive input, and it partly explains why chronic pain often persists and spreads even after the original injury has healed.
Pain Catastrophising
Pain catastrophising, the tendency to ruminate on pain, magnify its threat value, and feel helpless in relation to it, is the strongest psychological predictor of chronic pain outcomes and functional disability. Research by Michael Sullivan consistently demonstrates that catastrophising predicts pain intensity, disability, and treatment response more strongly than the severity of the physical injury. Reducing catastrophising through psychological intervention reliably reduces pain intensity and functional limitation, often without any change to the physical pathology.
Sources
- Moseley, G.L., & Butler, D.S. (2015). Fifteen years of explaining pain: the past, present, and future. Journal of Pain, 16(9), 807-813.
- Sullivan, M.J.L., et al. (2001). Theoretical perspectives on the relation between catastrophizing and pain. Clinical Journal of Pain, 17(1), 52-64.
- Woolf, C.J. (2011). Central sensitization: implications for the diagnosis and treatment of pain. Pain, 152(3 Suppl), S2-S15.