ObjectiveTo examine neuropsychological function, depression, and quality of life 6 months after discharge in patients who received mechanical ventilation in the intensive care unit.DesignProspective cohort study.SettingTertiary care, medical and coronary intensive care unit of a university-based medical center.Study PopulationA total of 275 consecutive, mechanically ventilated patients from a medical intensive care unit were prospectively followed. At 6 months, 157 were alive, of whom 41 (26%) returned for extensive follow-up testing.Measurement and Main ResultsNeuropsychological testing and assessment of depression and quality of life were performed at 6-month follow-up. Seven of 41 patients were excluded from further analysis due to preexisting cognitive impairment determined via surrogate interviews using the Modified Blessed Dementia Rating Scale and a review of medical records. On the basis of strict criteria derived from normative data, we found that 11 of 34 patients (32%) were neuropsychologically impaired. Impairment was generally diffuse but occurred primarily in areas of psychomotor speed, visual and working memory, verbal fluency, and visuo-construction. The rate of neuropsychological deficits in the study population was markedly higher than population norms for mild dementia. Scores on the Geriatric Depression Scale–Short Form were significantly more abnormal in the neuropsychologically impaired group than in the nonimpaired group at hospital discharge (p= .04) and at 6-month follow-up (p= .02), and clinically significant depression was found in 27% of impaired subjects at hospital discharge and in 36% at 6-month follow-up. No differences were observed between groups in quality of life as measured with the Short Form Health Survey-12 at discharge or 6-month follow-up.ConclusionsProlonged neuropsychological impairment is common among survivors of the medical intensive care unit and occurs with greater than anticipated frequency when compared with relevant normative data. Future investigations are warranted to elucidate the nature of the association between critical illness, neuropsychological impairment, depression, and decreased quality of life.