Diabetes is a long-term health condition. All individuals with diabetes should have access to psychological care and support to alleviate psychological suffering and promote self-management (Diabetes UK, 2022). Type 1 diabetes is usually diagnosed in childhood and affects both children and their families. However, to date, there had been very little research into psychological effects on primary-age children (8-11 years) and their carers. This thesis explored the relationship between mental health, well-being, and lifestyle of children with Type 1 diabetes and their healthy counterparts in Kuwait. It also investigated the effects that COVID-19 restrictions had on psychological functioning and lifestyle variables in childparent dyads. The thesis consists of three main sections. • Systematic reviews of the literature: These present what is known about psychological and lifestyle characteristics in children with Type 1 diabetes and their parents. It was concluded that most studies examined wide age ranges, and few were adequately powered with appropriate control groups. There was a gap in the literature for using developmentally appropriate, narrower age range and appropriate methodology to elucidate the psychological variables associated with Type 1 diabetes in children and the effects on parents, particularly when primary-age children are increasingly reported to have poor mental health. • A comparison study was conducted to investigate the link between the mental health, well-being, and lifestyle of 8-11-year-old children with Type 1 diabetes and their parents, as well as a healthy comparison group (N=200 dyads). It was concluded that children with Type 1 diabetes may experience more mental health and well-being concerns than their peers. Moreover, a relationship between higher BMI and poorer mental health was found in the diabetes group. It was concluded that concerns can be identified at a young age, which would be helpful in designing preventative interventions. However, no differences in mental health and well-being were detected between parents of children with Type 1 diabetes and parents of the control group. • COVID-19 study: The purpose of this study was to determine the effect of Kuwait's first lockdown on the mental health, well-being, and lifestyle of children with Type 1 diabetes and their parents (N=70 dyads). Baseline measures came from the diabetes cohort in the comparison study, and follow-up measures were administered a year later. The findings suggest that the COVID-19 lockdown had a significant psychological and possibly physiological effect on children and parents with Type 1 diabetes. As a result, there is a need for mental health support services tailored to these populations. Overall, the findings reported in this thesis add to the literature investigating psychological functioning of primary-age children with Type 1 diabetes and their parents, and call attention to the importance of healthy lifestyle, well-being, and mental health in this, previously under-researched, population.