QSPainRelief-STRAT

Inclusion Criteria: 1. Aged over 18 years. 2. Current treatment with an opioid for the treatment of pain, along with possible other drugs (see Table 1 for the list of eligible opioid medications - patients will be invited to indicate their treatment by selecting its name using a dropdown list). 3. Decision by the treating physician to introduce an additional non-opioid CNS-acting treatment such as an antiepileptic, an anti-depressant or benzodiazepine (see Table 2 for the list of eligible medications - patients will be invited to indicate their treatment by selecting its name using a dropdown list). 4. Capacity to understand and provide informed consent. Exclusion Criteria: 1. Insufficient French language skills. 2. Epilepsy treated by an anti-epileptic. 3. Alzheimer's disease. 4. Parkinson's disease 5. History of cancer diagnosed less than 5 years ago, treated by chemotherapy or radiotherapy.