Objective: The increasing use of opioids by patients suffering from chronic pain caused by different etiologies, and the possible effects of those substances on everyday activities, require careful evaluation of their effects. For this purpose, a systematic review was developed to assess the influence of opioids on the cognitive function in patients with chronic pain.
Methods: Eleven databases were analyzed using the following descriptors: opioids, opiates, narcotics, cognitive impairment, cognitive dysfunction, cognitive disorders and pain. The inclusion criteria were: clinical trials or case reports which included patients with chronic pain in treatment with opioids, cognitive assessment by specific tests and publication in English, Spanish or Portuguese.
Results: Sixteen surveys published between 1980 and 2004 met the criteria: six controlled trials, two randomized trials, and 10 studies of a lower scientific evidence level. All better quality controlled trials did not show cognitive impairment of patients under opioid therapy.
Conclusion: These results must be confirmed by additional randomized trials including a greater number of patients with chronic pain.