Parkinson’s disease (PD) is a common progressive neurological disorder with no cure. People with Parkinson’s (PwP) and their caregivers have to do many things to manage their health such as taking different medications, attending appointments and enacting lifestyle changes. This workload of healthcare and its impact is termed ‘treatment burden’, and the ability to manage this is termed ‘capacity’. The PD Life Study aimed for the first time to explore the treatment burden and capacity of PwP and their caregivers and identify key modifiable factors. Firstly, a systematic review and qualitative synthesis of 39 articles identified the main issues of treatment burden in PD which related to managing multiple medications, learning about PD and navigating healthcare obstacles. Secondly, semi-structured individual interviews with 17 PwP and caregivers (mean age=73 years) highlighted that difficulties with frequency and access to appointments, receiving appropriate levels of information, organising medications and life adaptations contributed to treatment burden. Aspects of capacity include the ability to drive, access to a car and technology, health literacy, living proximity to healthcare services, personal coping strategies, financial resources, and support from social networks. Thirdly, a national survey amongst 160 PwP (mean age=68 years) and 30 caregivers (mean age=69 years) found that 21% (N=34) of PwP and 50% (N=15) of caregivers reported high treatment burden levels on the Multimorbidity Treatment Burden Questionnaire. Higher treatment burden levels in PwP were associated with frailty, a higher number of non-motor symptoms and higher frequency of medications (>3 times a day). Female caregivers, those caring for someone with memory issues and caregivers with lower mental well-being scores were associated with higher caregiver treatment burden levels. Finally, three multi-stakeholder focus groups involving 11 participants (PwP, caregiver and healthcare professionals) discussed the key issues of treatment burden and capacity in PD and made recommendations for improvement. Better communication, expectation setting and appropriate signposting from healthcare professionals, increasing education and awareness of PD, improving flexibility of appointment structures and access to healthcare professionals, and embracing the role of technology were suggested changes at individual-provider and system-levels that could reduce treatment burden. This thesis has identified aspects of treatment burden and capacity of PwP and their caregivers related to managing appointments, obtaining satisfactory information, organising medications, and enacting lifestyle changes that could be modified to achieve better health outcomes in PD.