Abstract: We included 21 studies (16 cluster-RCTs, 4 CBAs and 1 cohort study) involving 1,092,877 participants (36,068 children and 1,056,809 adults) and 31,865 households in Africa, the Americas and South-East Asia in our meta-analyses and narrative synthesis. The 17 types of UCTs we identified, including one basic universal income intervention, were pilot or established government programmes or research experiments. The cash value was equivalent to 1.3% to 53.9% of the annualised gross domestic product per capita. All studies compared a UCT with no UCT, and three studies also compared a UCT with a CCT. Most studies carried an overall high risk of bias (i.e. often selection and/or performance bias). Most studies were funded by national governments and/or international organisations. Throughout the review, we use the words 'probably' to indicate moderate-quality evidence, 'may/maybe' for low-quality evidence, and 'uncertain' for very low-quality evidence. UCTs may not have impacted the likelihood of having used any health service in the previous 1 to 12 months, when participants were followed up between 12 and 24 months into the intervention (risk ratio (RR) 1.04, 95% confidence interval (CI) 1.00 to 1.09, P = 0.07, 5 cluster-RCTs, N = 4972, I² = 2%, low-quality evidence). At one to two years, UCTs probably led to a clinically meaningful, very large reduction in the likelihood of having had any illness in the previous two weeks to three months (odds ratio (OR) 0.73, 95% CI 0.57 to 0.93, 5 cluster-RCTs, N = 8446, I² = 57%, moderate-quality evidence). Evidence from five cluster-RCTs on food security was too inconsistent to be combined in a meta-analysis, but it suggested that at 13 to 24 months' follow-up, UCTs could increase the likelihood of having been food secure over the previous month (low-quality evidence). UCTs may have increased participants' level of dietary diversity over the previous week, when assessed with the Household Dietary Diversity Score and followed up 24 months into the intervention (mean difference (MD) 0.59 food categories, 95% CI 0.18 to 1.01, 4 cluster-RCTs, N = 9347, I² = 79%, low-quality evidence). Despite several studies providing relevant evidence, the effects of UCTs on the likelihood of being moderately stunted and on the level of depression remain uncertain. No evidence was available on the effect of a UCT on the likelihood of having died. UCTs probably led to a clinically meaningful, moderate increase in the likelihood of currently attending school, when assessed at 12 to 24 months into the intervention (RR 1.06, 95% CI 1.03 to 1.09, 6 cluster-RCTs, N = 4800, I² = 0%, moderate-quality evidence). The evidence was uncertain for whether UCTs impacted livestock ownership, extreme poverty, participation in child labour, adult employment or parenting quality. Evidence from six cluster-RCTs on healthcare expenditure was too inconsistent to be combined in a meta-analysis, but it suggested that UCTs may have increased the amount of money spent on health care at 7 to 24 months into the intervention (low-quality evidence). The effects of UCTs on health equity (or unfair and remedial health inequalities) were very uncertain. We did not identify any harms from UCTs. Three cluster-RCTs compared UCTs versus CCTs with regard to the likelihood of having used any health services, the likelihood of having had any illness or the level of dietary diversity, but evidence was limited to one study per outcome and was very uncertain for all three. This body of evidence suggests that unconditional cash transfers (UCTs) may not impact a summary measure of health service use in children and adults in LMICs. However, UCTs probably or may improve some health outcomes (i.e. the likelihood of having had any illness, the likelihood of having been food secure, and the level of dietary diversity), one social determinant of health (i.e. the likelihood of attending school), and healthcare expenditure. The evidence on the relative effectiveness of UCTs and CCTs remains very uncertain.

Plain-language summary: The evidence is current to May 2017. We included experimental and selected non-experimental studies of UCTs in people of all ages in LMICs. We included studies that compared participants who received a UCT with those who received no UCT. We looked for studies that examined health services use and health outcomes. We found 21 studies (16 experimental and 5 non-experimental ones) with 1,092,877 participants (36,068 children and 1,056,809 adults) and 31,865 households in Africa, the Americas and South-East Asia. The UCTs were government programmes or research experiments. Most studies were funded by national governments and/or international organisations. We use the words 'probably' to indicate moderate-quality evidence, 'may/maybe' for low-quality evidence, and 'uncertain' for very low-quality evidence. A UCT may not impact the likelihood of having used any health service in the previous 1 to 12 months. UCTs probably led to a clinically meaningful, very large reduction in the risk of having had any illness in the previous two weeks to three months. They may increase the likelihood of having had secure access to food over the previous month. They may also increase the average number of different food groups consumed in the household over the previous week. Despite several studies providing relevant evidence, the effects of UCTs on the likelihood of stunting and on depression levels remain uncertain. No study estimated effects on dying. UCTs probably led to a clinically meaningful, moderate increase in the likelihood of currently attending school. The evidence was uncertain for whether UCTs impacted livestock ownership, extreme poverty, participation in child labour, adult employment and parenting quality. UCTs may increase the amount of money spent on health care. The effects of UCTs on differences in health were very uncertain. We did not identify any harms from UCTs. Three experimental studies reported evidence on the impact of a UCT compared with a CCT on the likelihood of having used any health services, the likelihood of having had any illness or the average number of food groups consumed in the household, but evidence was limited to one study per outcome and was very uncertain for all three. Of the seven prioritised primary outcomes, the body of evidence for one outcome was of moderate quality, for three outcomes of low quality, for two outcomes of very low quality, and for one outcome, there was no evidence at all. This body of evidence suggests that unconditional cash transfer (UCTs) may not impact health services use among children and adults in LMICs. UCTs probably or may improve some health outcomes (i.e. the likelihood of having had any illness, the likelihood of having secure access to food, and diversity in one's diet), one social determinant of health (i.e. the likelihood of attending school), and healthcare expenditure. The evidence on the health effects of UCTs compared with those of CCTs is uncertain.