## 1 Introduction  
Huntington's disease (HD) is a progressive, autosomal dominant, inherited neurodegenerative disorder affecting as many as 13.7 per 100,000 individuals based on worldwide prevalence estimates [1; 2; 3]. The disease is caused by an expanded CAG triplet repeat in the huntingtin gene (HTT), which in turn leads to expression of a mutated toxic huntingtin protein [4]. Accumulation of this mutated protein leads to the gradual development of motor abnormalities (e.g., chorea, dystonia, dysarthria), progressive deterioration of cognitive processes (e.g., executive dysfunction, emotional regulation), and a variety of neuropsychiatric symptoms such as depression, which is considered a central component of HD [5] and affects an estimated 50% of patients [1; 6]. Typically, the onset of HD occurs in mid-life between 30-50 years of age, though symptoms can manifest as early as age 5 and as late as age 80+ [7].  
Due to the progressive nature of the disease, symptoms worsen over the lifespan, leading to increased dependency on care partners for performing daily activities [1; 8]. Thus, HDconfers increasing burden over time, both to patients (as a result of their worsening symptomatology) as well as to those who care for them. These humanistic burdens are myriad, impacting mental health, financial wellbeing, and inter-personal relationships [9; 10; 11; 12; 13; 14; 15].  
While the impacts of HD on patients and care partners have been a focus of prior research, these studies mostly describe the burdens in isolation, without contextualizing the experience of HD patients and care partners relative to those without neurodegenerative disease, or to those with a differing neurodegenerative disease. For example, Parkinson's disease (PD) is another progressive neurodegenerative condition that affects as many as 418 per 100,000 individuals based on worldwide prevalence estimates [16]. The disease is caused by the death of dopaminergic neurons in the substantia nigra, resulting in a variety of motor impairments (e.g., tremor, rigidity, bradykinesia), cognitive deficits (e.g., executive dysfunction, dementia), and psychological symptoms [17]. Like HD, roughly 50% of those with PD are estimated to have anxiety and/or depression [6; 18]; thus, both populations may benefit from psychiatric interventions for improving quality of life [19; 20]. Despite their different etiologies, comparisons between PD and HD can highlight the unique and shared burdens of these conditions and inform the design of interventions to effectively offset these burdens to both patients and care partners. These comparisons also may inform resource allocation and inform clinical care teams on how to better advise and prepare patients and their families for the sequelae associated with HD.  
In the absence of effective disease-modifying or curative therapies and interventions for HD [21; 22], efforts to improve health-related quality of life (HRQoL) and mental health must focus on actionable, real-world targets. Here, we aimed to evaluate the humanistic and clinical burdens reported among manifest individuals with HD and HD care partners, including the occurrence of comorbid mental health conditions, their severity, and overall impacts on HRQoL. These results are contextualized against adults and care partners selected from two relevant populations: the broader, non-neurodegenerative General Population, and a second neurodegenerative population (Parkinson's Disease). The aim is to identify the shared as well as unique or incremental burdens that are experienced by those with HD as compared to those with Parkinson's Disease or the General Population, thereby informing burden-modifying approaches for management of HD.