Background: During intensive care unit (ICU) admission, patients and their carers experience physical and psychological stressors that may result in psychological conditions including anxiety, depression, and post-traumatic stress disorder (PTSD). Improving communication between healthcare professionals, patients, and their carers may alleviate these disorders. Communication may include information or educational interventions, in different formats, aiming to improve knowledge of the prognosis, treatment, or anticipated challenges after ICU discharge., Objectives: To assess the effects of information or education interventions for improving outcomes in adult ICU patients and their carers., Search Methods: We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, CINAHL, and PsycINFO from database inception to 10 April 2017. We searched clinical trials registries and grey literature, and handsearched reference lists of included studies and related reviews., Selection Criteria: We included randomised controlled trials (RCTs), and planned to include quasi-RCTs, comparing information or education interventions presented to participants versus no information or education interventions, or comparing information or education interventions as part of a complex intervention versus a complex intervention without information or education. We included participants who were adult ICU patients, or their carers; these included relatives and non-relatives, including significant representatives of patients., Data Collection and Analysis: Two review authors independently assessed studies for inclusion, extracted data, assessed risk of bias, and applied GRADE criteria to assess certainty of the evidence., Main Results: We included eight RCTs with 1157 patient participants and 943 carer participants. We found no quasi-RCTs. We identified seven studies that await classification, and three ongoing studies.Three studies designed an intervention targeted at patients, four at carers, and one at both patients and carers. Studies included varied information: standardised or tailored, presented once or several times, and that included verbal or written information, audio recordings, multimedia information, and interactive information packs. Five studies reported robust methods of randomisation and allocation concealment. We noted high attrition rates in five studies. It was not feasible to blind participants, and we rated all studies as at high risk of performance bias, and at unclear risk of detection bias because most outcomes required self reporting.We attempted to pool data statistically, however this was not always possible due to high levels of heterogeneity. We calculated mean differences (MDs) using data reported from individual study authors where possible, and narratively synthesised the results. We reported the following two comparisons.Information or education intervention versus no information or education intervention (4 studies)For patient anxiety, we did not pool data from three studies (332 participants) owing to unexplained substantial statistical heterogeneity and possible clinical or methodological differences between studies. One study reported less anxiety when an intervention was used (MD -3.20, 95% confidence interval (CI) -3.38 to -3.02), and two studies reported little or no difference between groups (MD -0.40, 95% CI -4.75 to 3.95; MD -1.00, 95% CI -2.94 to 0.94). Similarly, for patient depression, we did not pool data from two studies (160 patient participants). These studies reported less depression when an information or education intervention was used (MD -2.90, 95% CI -4.00 to -1.80; MD -1.27, 95% CI -1.47 to -1.07). However, it is uncertain whether information or education interventions reduce patient anxiety or depression due to very low-certainty evidence.It is uncertain whether information or education interventions improve health-related quality of life due to very low-certainty evidence from one study reporting little or no difference between intervention groups (MD -1.30, 95% CI -4.99 to 2.39; 143 patient participants). No study reported adverse effects, knowledge acquisition, PTSD severity, or patient or carer satisfaction.We used the GRADE approach and downgraded certainty of the evidence owing to study limitations, inconsistencies between results, and limited data from few small studies.Information or education intervention as part of a complex intervention versus a complex intervention without information or education (4 studies)One study (three comparison groups; 38 participants) reported little or no difference between groups in patient anxiety (tailored information pack versus control: MD 0.09, 95% CI -3.29 to 3.47; standardised general ICU information versus control: MD -0.25, 95% CI -4.34 to 3.84), and little or no difference in patient depression (tailored information pack versus control: MD -1.26, 95% CI -4.48 to 1.96; standardised general ICU information versus control: MD -1.47, 95% CI -6.37 to 3.43). It is uncertain whether information or education interventions as part of a complex intervention reduce patient anxiety and depression due to very low-certainty evidence.One study (175 carer participants) reported fewer carer participants with poor comprehension among those given information (risk ratio 0.28, 95% CI 0.15 to 0.53), but again this finding is uncertain due to very low-certainty evidence.Two studies (487 carer participants) reported little or no difference in carer satisfaction; it is uncertain whether information or education interventions as part of a complex intervention increase carer satisfaction due to very low-certainty evidence. Adverse effects were reported in only one study: one participant withdrew because of deterioration in mental health on completion of anxiety and depression questionnaires, but the study authors did not report whether this participant was from the intervention or comparison group.We downgraded certainty of the evidence owing to study limitations, and limited data from few small studies.No studies reported severity of PTSD, or health-related quality of life., Authors' Conclusions: We are uncertain of the effects of information or education interventions given to adult ICU patients and their carers, as the evidence in all cases was of very low certainty, and our confidence in the evidence was limited. Ongoing studies may contribute more data and introduce more certainty when incorporated into future updates of the review.