Confounders in anaesthesia-related depression outcomes

Abstract

We read with great interest the study by Ho et al., which provides valuable insights into the long-term effects of anaesthesia choice on postoperative outcomes [1]. However, several potential confounders influencing the link between anaesthetic techniques and postoperative depression were not specifically addressed in the analysis.

First, pre-existing mental health conditions, such as a history of depression or anxiety, are established risk factors for postoperative depression. These conditions may also impact the choice of anaesthesia due to concerns around peri-operative psychological stress [2]. Additionally, socio-economic status, another crucial determinant of health, could confound the relationship between anaesthesia type and depression. Patients with lower socio-economic status may have limited access to certain anaesthesia options or an increased baseline risk of depression, irrespective of surgical factors [3].

Second, chronic pain and the severity of pre-operative pain are important considerations. Over half of surgical patients experience inadequate postoperative pain management. Certain pre-operative psychological interventions can mitigate acute postoperative pain scores and reduce opioid consumption [4]. Social support and living conditions, although unmeasured confounders, also play a significant role. Social isolation and limited support networks are indirectly linked to surgical outcomes through their association with depression, which is itself associated with poorer outcomes [5]. These psychosocial factors may also impact the choice of anaesthesia.

Finally, reliance on ICD-10 codes for diagnosing depression may result in an underestimation of its true incidence, as mental health disorders are frequently underdiagnosed or misclassified in clinical settings. This potential underreporting could distort the observed differences between anaesthesia groups, particularly if diagnostic practices vary among contributing institutions.

To strengthen future research, incorporating validated mental health assessments pre- and post-surgery, as well as collecting data on socio-economic factors and social support networks could provide a more nuanced understanding of anaesthesia's role in postoperative depression. Although the authors used propensity score matching, residual confounding from unobserved variables remains possible. Future research should include these factors to improve validity.

We commend Ho et al. for their contribution and hope our discussion helps in the planning of future research, such as multicentre cohort studies that could include psychosocial factors such as social support and economic status.