Systematic review Table 2 Continued Network feature Network stability Reciprocity Social capital Social climate Key structural ﬁndings for health network quality and safety Network stability is related to network effectiveness, and can moderate the impact of resources Longitudinal SNA can measure network expansion, with decreased fragmentation increasing potential information ﬂow Reciprocity of ties shows whether there is a hierarchical (low reciprocity) or horizontal (high reciprocity) structure in the professional network Organisational social capital, in addition to professional experience and workload, can predict overall job satisfaction Social inﬂuence of peer professionals has a greater impact than social capital on health professional performance Positive social climate protects nurses against burnout Professional and social networks and support do not mitigate against work stress of chief manager nurses or physician clinical directors Studies Milward and Provan (2003),47 Mendel et al (2009)34 Creswick and Westbrook (2007),30 Creswick et al (2009)31 Ommen et al (2009),48 Fattore et al (2009)39 Garrett and McDaniel (2001),49 Lindholm (2006),50 Lindholm et al (2003),51 Lindholm et al (2004)52 Based on our quality assessment criteria (see online supplement, table S3), the quality ratings of the studies are provided in the online appendix (table B). Fourteen studies (54%) were assessed as meeting all of the quality assessment criteria relevant to their study design. Ten studies (39%) met almost all of the criteria, and those criteria that were not fulﬁlled were thought unlikely to alter the conclusions of the study. In two studies (7%), some of the criteria were fulﬁlled, and those criteria that were not fulﬁlled were thought unlikely to alter the conclusions of the study. We did not include studies that met few or no quality assessment criteria. The level of analysis is a key area of interest in network studies. There are three principal levels: the actor/s level, the network (or organisation) level and the inter- network (or inter-organisation) level. Seventeen studies were directed at two levels, the actors and the network (three looked at the actors and team), eight studies examined networks and one examined all three levels. Four main areas of structural relationships were studied: structural relationships within and between organisa- tions; health professionals and social context; structure of quality collaboratives and healthcare partnerships; and structure in knowledge sharing networks. Table 2 summarises the key network features examined by indi- vidual studies, and identiﬁes the substantive structural ﬁndings for health network quality and safety, in relation to those network features. Structural relationships within and between organisations Six studies examined structural relationships within and between networked organisations, including two of dementia provider networks, three of mental health provider networks (one comparing rural and urban 244 relationships) and one of a hospital network. Carpentier et al54 used comparative case studies of seven organisa- tions to examine relationships between the networks providing assistance to community patients with early- stage dementia in Montreal, Canada. The three inter- action levels (interactions between practitioners and caregivers, internal structures and linkages between groups) were found to determine the quality of the practitionerecaregiver interface. Another Canadian case study on dementia care45 evaluated the effectiveness of four community-based dementia care networks in Ontario. SNA identiﬁed patterns of administrative and clinical exchanges among networked agencies. Exchanges between groups of agencies (cliques) within each of the four networks were more important than those between individual agencies within each network. In seminal work examining network structure and effectiveness in the health sector, Milward and Provan46 47 used SNA to examine structural relationships in networks of provider organisations in two studies. The 1998 research included four city community mental health networks and one youth substance-abuse prevention network. Each of the four mental health networks was well integrated, based on two measures e organisational links and cooperative links. With the substance-abuse prevention network, SNA helped to identify agencies not well linked to the system. Milward and Provan47 then used SNA on the results of the initial research, along with a 4-year study of one of the four networks, to evaluate collaboration and contracting strategies. The relationship between network structure and effectiveness was mediated by the context within which services were provided, with resource muniﬁcence and network stability identiﬁed as the two contextual BMJ Qual Saf 2012;21:239e249. doi:10.1136/bmjqs-2011-000187