Subcortical ischemic depression, also known as vascular depression, is a medical condition most commonly seen in older people with major depressive disorder. Subcortical ischemic depression refers to vascular depression specifically due to lesions and restricted blood flow, known as ischemia, in certain parts of the brain. However, the disorder is typically described as vascular depression in the literature. There is no formal and accepted definition of vascular depression and the hypothesis requires further research to support the causal link between these vascular lesions and depression. Thus, it is difficult to determine if vascular depression can be considered a distinct sub-type of major depressive disorder (MDD). However, with current criteria, some studies estimate that vascular depression may account for over half of the cases of MDD in the elderly.
Diagnosis Vascular depression is typically diagnosed using either magnetic resonance imaging (MRI) or clinically defined criteria. MRI-defined vascular depression is more commonly referred to as subcortical ischemic depression (SID) and emphasizes the relationship between MRI identification of lesions in the brain and depressive symptoms. An alternative definition is depression executive dysfunction (DED) syndrome and focuses on the link between clinical symptoms of cardiovascular risk and depressive symptoms. Both of these competing definitions are supported in the literature and provide a strategy to diagnose vascular depression. The criteria for MRI-defined vascular depression focus on the presence and severity of either deep white matter lesions, often referred to as white matter hyperintensities, or subcortical grey matter lesions. The most severe lesion in an individual is scored based on predefined criteria and considered in combination with two measures of depressive symptomology. These white matter lesions are thought to disrupt emotional and cognitive functioning. Alternatively, clinically defined criteria as proposed initially by Alexopoulos and colleagues (1997) includes dimensions of depressive symptoms, disability, and cognitive impairment. Specifically, DED syndrome has been characterized by a loss of interest in activities, psychomotor retardation, paranoia, and cognitive impairment in the domains of language fluency and visual naming. Aizenstein and colleagues (2016) proposed diagnostic criteria for vascular depression that incorporate elements of both clinical and MRI-definitions. These diagnostic criteria are:
Evidence of vascular pathology in elderly subjects with or without cognitive impairment Absence of previous depressive episodes preceding obvious cerebrovascular disease Presence of cerebrovascular risk factors Co-incidence of depression with cerebrovascular risk factors Clinical symptoms characteristic of vascular depression such as executive dysfunction, decrease in processing speed, and lethargy Neuroimaging data confirming cerebrovascular disease Studies have not yet been conducted using this set of criteria, so it is unclear whether it provides an advantage over current standards. Some aspects of the criteria are not always necessary to diagnose individuals. For example, one study found that late-onset depression, executive dysfunction, and subcortical gray lesions in individuals were useful for identifying vascular depression, but only the presence of deep white matter lesions was necessary to classify individuals as having the disorder.
Distinction from major depressive disorder There is inadequate evidence to support vascular depression as a distinct subtype of major depressive disorder due to mixed results. Specifically, it is difficult to differentiate a diagnosis of vascular depression from similar diagnoses, such as post-stroke or late-life depression. Some researchers suggest that vascular depression may be too restricted in its definition and proposed etiology. However, there is some evidence of internal validity of vascular depression which provides initial support for its classification as a unique subtype. The most distinctive symptoms of vascular depression compared to non-vascular depression include increased cognitive and executive impairment, proposed to be associated with cerebrovascular risk factors. Additionally, studies have reported that when compared to individuals with non-vascular depression, those diagnosed with vascular depression tend to be older, have a lower family history of mental illness, and have a history of hypertension. Individuals with vascular depression also tend to have more deficits in self-initiation and concentration, higher cardiac illness burden and cerebrovascular risk factors, cognitive impairment (as associated with the severity of white matter lesions in the brain), and increased treatment resistance. Those with vascular depression have also reported increased lassitude, which is described as a difficulty getting started in the morning and may be related to fatigue. An additional study found that individuals with vascular depression reported greater executive dysfunction and apathy compared to both nondepressed individuals with vascular disease and healthy control participants. This provides support that these symptoms may be a result of vascular depression specifically and not solely individuals’ vascular disease.
Cause
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