Significant psychological impacts, including post-traumatic stress disorder (PTSD), have been associated with patients under sedation in intensive care units (ICUs). However, it remains unknown if and how sedation is related to post-ICU psychological outcomes. This literature review explores the relationships between sedation, the depth of sedation and psychological disorders. A review of existing literature was undertaken systematically with key terms and included peer-reviewed primary research and randomised controlled trials (RCTs). To ensure subject relevance pre-2006, non-English and paediatric-based research was excluded. Findings highlighted that reduced sedation levels did not significantly reduce the outcome of PTSD, yet reduced ICU length of stay and length of mechanical ventilation (MV) were both associated with lighter sedation. Further research is recommended into more specific factual and delusional memories post ICU in relation to the level of sedation and to psychological distress.