The quality of caregiving in early infancy and childhood is one of the most important predictors of child outcome. The caregiving relationship is often compromised when mothers are unable to attend to their infants’ needs due to their own experiences of childhood trauma, maternal stress, mental health difficulties, and other environmental adversities. One particular group who experience many, if not all of these adversities, are mothers with substance misuse problems. The outcomes for their children are consistently poor. These difficulties emerge in early years, when infants and young children live in chaotic environments, and at times, with mothers who are unable to provide sensitive and responsive caregiving. Given the extensive literature documenting the link between early caregiving and child developmental outcome, it is not surprising that there has been a significant research effort investigating the quality of caregiving in substance abusing mothers. This thesis began with a focus on substance misusing mothers as a high-risk group. Research studies examining the quality of caregiving in mothers with substance use problems have had inconsistent findings. There are many studies that find poor quality caregiving in mothers with substance misuse compared to non-substance misusing mothers, while other studies find relatively little difference between groups. However, there is considerable variability across studies. Quality of study design is highly variable with a number of studies drawing comparison groups from community populations that differ from the substance misusing group on a range of demographic factors. The ages of the children range from birth to toddlerhood and a number of studies use mothers in treatment as their reference group. In the light of the diverse findings in the extant literature, the aim of Study 1 was to assess the extent to which mothers with substance misuse have compromised caregiving. To this end a systematic review and meta-analysis of research studies spannng two decades (1995 - 2015; final update prior to publication) was undertaken. The initial search was undertaken from Scopus, MEDLINE, Science Direct, PsycINFO, SpringerLink and Google Scholar and identified 2028 potential studies. Twenty four studies met the following inclusion criteria: mothers with children aged birth to 40 months; mothers currently using illicit substance misusers and/or were on opioid replacement therapy due to a history of opioid dependence and/or were in residential treatment due to a history of illicit substance use; a comparison group of non-substance using mothers; and maternal-child interactions were assessed using an observational method that was videotaped and coded to rate maternal caregiving quality The key outcomes were measures of two constructs (i) maternal sensitivity and (ii) child responsivity. A global meta-analysis for maternal sensitivity (n = 24 studies) and child responsiveness (n = 16 studies) on 3433 mother-infant dyads yielded significant population effect sizes and significant heterogeneity. Using subgroup analyses, heterogeneity was significantly reduced when studies were grouped by design (i.e., participants matched versus not matched on key demographic characteristics). Substance misusing mothers were still significantly poorer on scores of maternal sensitivity compared with their matched counterparts, but the effect size was significantly smaller. These results highlighted that compromised caregiving is found in high-risk mothers, and a common factor impacting maternal caregiving was shared environmental adversity. Thus, Study 2 set out to compare the quality of caregiving in three groups: substance misusing mothers, mothers matched in socioeconomic characteristics and mothers drawn from a community sample. There is extensive evidence linking maternal substance misuse with compromised caregiving of young infants. However, there is also widely documented evidence that other psychosocial risk factors, childhood trauma, maternal psychopathology and environment characterised by financial and social disadvantage are also predictive of poor caregiving. As mothers with substance misuse problems share many of these risk factors, it is possible that compromised caregiving, including the quality of the parent-child relationship, is attributable to these co-occurring factors. Hence, the second aim was to investigate a potential pathway in which factors associated with compromised caregiving could be tested; specifically, if there was a pathway from childhood trauma to caregiving quality that was mediated by environmental risk factors and borderline personality features. A total sample of 51 Australian mothers and their children (12-42 months) participated in this study: 17 mothers currently in treatment for opioid and/or ploy-substance dependence; 17 mothers matched on years of education, source of income, maternal age and child age reporting no current substance misuse; and 17 mothers reporting no substance misuse history matched on maternal age and child age only. Assessment duration was 90-120 minutes and consisted of completion of measures and videotaping of a 20 minutes mother-child interaction. Results showed that (i) there was no significant difference between the two high-risk groups of mothers but (ii) there were significant differences on all key variables between the two high risk mothers and the community sample; and (iii) irrespective of substance misuse, the relationship between exposure to childhood trauma and quality of caregiving was mediated via environmental risk but not severity of borderline personality features. Study 3 extended these findings by further investigating the association between maternal childhood trauma, borderline personality features, environmental risk, quality of caregiving and child developmental outcome in a sample of mother-infant dyads, oversampling for at-risk mothers (N= 125). Method of collecting data was the same as for Study 2. The model tested was a serial mediation model, in which the association between maternal childhood trauma and child developmental outcome was proposed to be influenced by the extent to which mothers experience personality pathology and ongoing exposure of environmental risk, in turn impacts on her capacity to provide optimal caregiving to her child. In this model, two out of seven potential pathways tested in the serial PROCESS mediation analysis were significant. The pathway between childhood adversity and child developmental outcomes via borderline personality, environmental risk and caregiving quality was supported, along with the pathway from childhood adversity to child development outcomes via borderline personality and environmental risk. Overall, the current thesis advances the substance misuse, childhood adversity, trauma and attachment literature in several important ways. Firstly, the thesis presented a comprehensive review and meta-analysis of the available studies examining caregiving quality in mothers using illicit substances (Study 1). This review highlighted the potential for future research to investigate the potential mechanisms that underpin the development of poor caregiving in a population of mothers sampled for high risk including substance misuse, conducted via Study 2. Study 3 extended on findings from Study 2, investigating the potential underlying mechanisms or causal pathways that may be implicated in the development of compromised caregiving and child outcomes. In summary, the thesis findings highlight the importance of identifying and understanding the mechanisms that impact quality caregiving and child outcomes in high-risk families. This in turn, informs how interventions can be designed (e.g., trauma focused care) and underscores the importance of early intervention to counteract the impact of environmental adversity and maternal childhood trauma on quality of caregiving. These findings have important implications for future research, policy design, intervention planning, and clinical practices.