Pain

Pain is caused by activation of nociceptors by potentially damaging stimuli, including extremes of temperature and pressure and injury-related chemicals. The literature also supports pain arising or being amplified in association with opioid exposure, depression, and long COVID, but these are described as associated contexts rather than sole causes.

Pain begins when specialized peripheral sensory neurons transduce noxious stimuli into electrical signals that are relayed to higher brain centers. The literature also describes modulation through nociception, neuronal plasticity, signal transduction, synaptic transmission, excitatory postsynaptic potentials, and top-down central circuits, with shared biological pathways and neurotransmitters such as serotonin and inflammatory mediators including cytokines and tumor necrosis factor-alpha.

Factors associated with greater pain burden include depression, moderate to severe pain, impaired function, and refractory symptoms. Emotional state, anxiety, attention and distraction, past experiences, and memories can also enhance the pain experience, and opioid exposure is associated with opioid-induced hyperalgesia.

The grounding supports drug therapy as a general management modality, but does not specify a particular standard regimen. The literature also points to broader management of pain comorbidity and modulation, including approaches informed by neurotransmitter and inflammatory pathways, but not to a specific drug class as universal standard of care.