Apathy in Huntington’s Disease: A Review of the Current Conceptualization

Apathy is one of the most common psychiatric symptoms experienced by patients with Huntington’s disease (HD). It appears early, progresses with the disease course and has been shown to contribute significantly to caregiver burden. However, what is understood by apathy in HD is not clearly defined nor the underlying mechanisms responsible for it. In this review, we discuss the concept of apathy in the context of HD and propose that a consensus regarding its conceptualisation and subsequently its diagnostic criteria would significantly benefit the field. In order to undertake this work, we began by reviewing the existing literature on the definition and assessment of apathy in HD, its underlying neurobiological basis and its relationship to other related features such as abulia, anhedonia and alexithymia. In the context of HD, apathy could be described by a loss of or diminished motivation, emotion and goal-directed behaviour that is not best explained by motor or social constraints of the disease. However, there is an urgent need to better understand the characteristics of apathy specifically in HD, how they evolve across the disease course and how they relate to central dopaminergic pathways. Only by undertaking such work can we hope to better understand this early and disabling aspect of HD.