Living with untreated depression can complicate many chronic conditions
including stroke, heart disease, and diabetes [1-2]. The estimated percentage of the
United States (US) adults suffering from Major Depressive Disorder (MDD) is 3%, or
approximately 9 million people [3]. Among those suffering from chronic
neurodegenerative disorders, such as Alzheimer’s (AD), Huntington disease (HD), and
Parkinson’s disease (PD) and amyotrophic lateral sclerosis (ALS), the rates of MDD are
considerable higher [4-7].
Clinically significant depressive disturbances are estimated to affect 40-50% of
patients with PD [5], and 24.8% are thought to suffer from MDD [8]. MDD is considered
the most common symptom among pre-symptomatic Huntington disease carriers [9] with
an estimated prevalence of 25% [6]. However, there is still some debate as to whether the
prevalence increases with progression of Huntington disease or not [6; 10-11]. The
estimated prevalence of MDD in patients suffering ALS is 16 - 25% [7].
The prevalence of depression in those suffering from dementia has been reported
as 29% [12]. Specifically, the prevalence of MDD in individuals with AD has been
estimated to be 5 - 23% [4; 13]. In a retrospective cohort study conducted in the US, the
prevalence of depression was found to be higher in patients with vascular dementia than
AD [4].
This association between depression and neurodegenerative conditions indicates
the importance of appropriate recognition and treatment of depression in these patient
populations, but also begs the question of potential causation.
