Abstract: The 2016 update included two more studies (n = 196) and more publications with additional data for four already included studies. The updated review therefore includes 7524 participants from 40 randomised controlled trials (RCTs). We found data relevant to two comparisons: ICM versus standard care, and ICM versus non-ICM. The majority of studies had a high risk of selective reporting. No studies provided data for relapse or important improvement in mental state. 1. ICM versus standard care When ICM was compared with standard care for the outcome service use, ICM slightly reduced the number of days in hospital per month (n = 3595, 24 RCTs, MD -0.86, 95% CI -1.37 to -0.34,low-quality evidence). Similarly, for the outcome global state, ICM reduced the number of people leaving the trial early (n = 1798, 13 RCTs, RR 0.68, 95% CI 0.58 to 0.79, low-quality evidence). For the outcome adverse events, the evidence showed that ICM may make little or no difference in reducing death by suicide (n = 1456, 9 RCTs, RR 0.68, 95% CI 0.31 to 1.51, low-quality evidence). In addition, for the outcome social functioning, there was uncertainty about the effect of ICM on unemployment due to very low-quality evidence (n = 1129, 4 RCTs, RR 0.70, 95% CI 0.49 to 1.0, very low-quality evidence). 2. ICM versus non-ICM When ICM was compared with non-ICM for the outcome service use, there was moderate-quality evidence that ICM probably makes little or no difference in the average number of days in hospital per month (n = 2220, 21 RCTs, MD -0.08, 95% CI -0.37 to 0.21, moderate-quality evidence) or in the average number of admissions (n = 678, 1 RCT, MD -0.18, 95% CI -0.41 to 0.05, moderate-quality evidence) compared to non-ICM. Similarly, the results showed that ICM may reduce the number of participants leaving the intervention early (n = 1970, 7 RCTs, RR 0.70, 95% CI 0.52 to 0.95,low-quality evidence) and that ICM may make little or no difference in reducing death by suicide (n = 1152, 3 RCTs, RR 0.88, 95% CI 0.27 to 2.84, low-quality evidence). Finally, for the outcome social functioning, there was uncertainty about the effect of ICM on unemployment as compared to non-ICM (n = 73, 1 RCT, RR 1.46, 95% CI 0.45 to 4.74, very low-quality evidence). 3. Fidelity to ACT Within the meta-regression we found that i.) the more ICM is adherent to the ACT model, the better it is at decreasing time in hospital ('organisation fidelity' variable coefficient -0.36, 95% CI -0.66 to -0.07); and ii.) the higher the baseline hospital use in the population, the better ICM is at decreasing time in hospital ('baseline hospital use' variable coefficient -0.20, 95% CI -0.32 to -0.10). Combining both these variables within the model, 'organisation fidelity' is no longer significant, but the 'baseline hospital use' result still significantly influences time in hospital (regression coefficient -0.18, 95% CI -0.29 to -0.07, P = 0.0027). Based on very low- to moderate-quality evidence, ICM is effective in ameliorating many outcomes relevant to people with severe mental illness. Compared to standard care, ICM may reduce hospitalisation and increase retention in care. It also globally improved social functioning, although ICM's effect on mental state and quality of life remains unclear. Intensive Case Management is at least valuable to people with severe mental illnesses in the subgroup of those with a high level of hospitalisation (about four days per month in past two years). Intensive Case Management models with high fidelity to the original team organisation of ACT model were more effective at reducing time in hospital. However, it is unclear what overall gain ICM provides on top of a less formal non-ICM approach. We do not think that more trials comparing current ICM with standard care or non-ICM are justified, however we currently know of no review comparing non-ICM with standard care, and this should be undertaken.

Plain-language summary: We carried out electronic searches for randomised controlled trials comparing ICM with non-ICM or standard care in 2009, 2012, and 2015. We included 40 trials involving 7524 people. The trials took place in Australia, Canada, China, Europe, and the USA. When ICM was compared to standard care, those in the ICM group were more likely to stay with the service, have improved general functioning, get a job, not be homeless, and have shorter stays in hospital (especially when they had had very long stays in hospital previously). When ICM was compared to non-ICM, the only clear difference was that those in the ICM group were more likely to be kept in care. None of the evidence for the main outcomes of interest was high quality; at best the evidence was of moderate quality. In addition, the healthcare and social support systems of the countries where the studies took place were quite different, so it was difficult to make valid overall conclusions. Furthermore, we were unable to use much of the data on quality of life and patient and carer satisfaction because the trials used many different scales to measure these outcomes, some of which were not validated.  The development of an overall scale and its validation would be very beneficial in producing services that people favour. (Plain language summary initially prepared for this review by Janey Antoniou of RETHINK, UK (rethink.org))