Why context changes pain: the biopsychosocial model explained

For most of the 20th century, medicine ran on a simple formula: find the structural problem, fix it, pain goes away. The biomedical model. For acute injuries and infections, it works reasonably well.

But in 1977, psychiatrist George Engel published a landmark paper arguing this model was fundamentally inadequate. Biology alone couldn't explain illness, suffering, or recovery. He proposed the biopsychosocial model: health and illness are products of the interaction between biological, psychological, and social factors.

The biological dimension covers the tissue itself — the injury, the inflammation, the nociceptive input. This is what most imaging and clinical tests pick up.

The psychological dimension includes thoughts, beliefs, emotions, and behaviours. Fear of movement, catastrophising, depression, and anxiety all independently predict pain intensity and recovery outcomes. These aren't peripheral concerns — they're central drivers.

The social dimension covers work demands, family relationships, financial stress, cultural beliefs about pain, and the messages received from the healthcare system. Being told "your spine is crumbling" by a well-meaning clinician can extend disability for months.

Orthopaedic surgeon Gordon Waddell helped translate the biopsychosocial model into clinical practice. His work identified "yellow flags" — psychosocial risk factors that predict poor recovery from low back pain.

These include believing that pain signals damage and rest is the answer, having a physically demanding job or low job satisfaction, negative emotions around the injury, and passive coping strategies. The more yellow flags present, the higher the risk of chronic disability — regardless of what the scan shows.

This is not about blame. These are modifiable factors. Identifying them early means treatment can address them directly.

One night of poor sleep measurably increases pain sensitivity the next day — that's reproducible in lab settings. Ongoing psychological stress keeps the nervous system in threat mode, which amplifies pain signals. And beliefs about pain — whether it means something is seriously wrong, whether movement is safe — directly affect how the brain interprets nociceptive input.

In my clinic, I routinely ask about sleep, stress, and what a patient thinks their pain means. Not because I'm ignoring their biology — but because those factors are often doing more work than the disc bulge on the scan.