Depressive cognitive disorders, also called Pseudodementia (a term founded by Kiloh in the year 1961), is defined as the cognitive and functional impairment imitating neurodegenerative disorders caused secondary to neuropsychiatric symptoms. Depression with cognitive impairment was given less significance in the past. Though the current practice has given heightening attention to these disorders, as it has been found that the cognitive symptoms associated with depression persist, as residual symptoms (in addition to mood symptoms), and in some cases transform into true neurocognitive dementia over time, these cognitive distortions affect the functioning considerably and increase the risk of recurrence of a depressive disorder in the patients.
Since the 1980s, depressive cognitive disorders have been incorporated as part of the reversible and treatable forms of dementia, and in the 1990s, it became more noticeable that depression with the cognitive distortion can be the prodromal phase of neurodegenerative dementia that is irreversible. Recent research studies found that a depressive disorder is correlated with a heightened risk and acts as a strong predictor of developing true dementia. Depression with cognitive impairment nearly always implies incipient dementia and should prompt the professional to begin a relevant diagnostic workup. Based on these findings, the term pseudodementia has been strongly criticized and is considered inappropriate and misleading.
According to the diagnostic and statistical manual of mental disorders, fifth edition (DSM-5) cognitive impairment like difficulty thinking, concentrating and decision making are categorized as core symptoms of depression, but a description of reversible dementia secondary to neuropsychiatric disorders’ is not yet considered as a formal diagnosis in the classification system. In the elderly population, two distinct forms of mixed mood and cognitive disruptions are found. They can present with a preliminary mood disorder associated with cognitive disruption, or they can present with a preliminary dementing disorder that is associated with depression. Numerous overlapping characteristics make it difficult to distinguish the two. The connection between depressive disorder and neurodegenerative dementia is complicated and intricate. Cognitive impairment has been found to be persistent even after the depressive phase has remitted. The entire picture becomes more challenging when the depression is part of a bipolar disorder.
Mania in the elderly also has atypical presentation as compared to younger patients. They are often misdiagnosed as having dementia (Manic Pseudodementia) secondary to the pressured speech, and hyperkinesis is seen in manic elderly patients.
Although in current practice, the term pseudodementia has been considered redundant and misleading, its concept inaugurated a useful principle that every physician should think of depression as an etiology in a patient presenting with symptoms of neurodegenerative dementia and vice verse before formulating the final diagnosis.
Over the years, pseudodementia has remained valuable in promoting discussion of numerous treatable neuropsychiatric symptoms, but in recent times its use is strongly condemned in clinical practice. Despite the fact that it helps clinicians to think about treatable and reversible causes of dementing illness, it has major limitations. It implies that the patient has either an organic disorder or a functional impairment, but most of the patients have components of both. It is a descriptive term and should not be used as a diagnostic category. ’cognitive impairment’ has been proposed to be used instead of pseudodementia.
The long-term persistence of inflammatory processes leads to cognitive deficits in depression. It is presented in two different forms— ‘depressive cognitive disorders’ or the ‘Wernicke pseudodementia.’ The latter is considered a more severe form.
Depression is the dominating cause of memory loss in the elderly population. Numerous factors contribute to the development of depressive cognitive disorders:
The prevalence of a major depressive disorder in the elderly population varies between 30% and 45%. Out of these, 10-12% of the patients get admitted to an acute care setting, and 12% to 14% get admitted to a nursing home. The cognitive impairment has been documented to be 85% to 94% of the time during an acute depressive episode and 39% to 44% of the time after recovery of the depressive episode. On the other hand, neurodegenerative dementia is accompanied by depression in 15% to 23% of cases. Research shows 20% to 30% of executive function deficits in depressed individuals.
The pathophysiology of depressive cognitive disorders is originated from the underlying neuropsychiatric disorder. Due to the overlapping signs and symptoms of depression and dementia, it becomes difficult to discern the exact pathology of cognitive impairment. Numerous cognitive deficits are found in late-onset depression. Among those, memory impairment (anterograde and retrograde) is extensively analyzed for the evaluation of cognitive distinctions in depressive disorder and dementia. Major depressive disorder depicts a multitude of deficits in the spheres of episodic memory, including explicit vocal and visual memory domains. The implicit memory functions are preserved. This memory impairment is secondary to the temporal lobe abnormality seen in a depressive disorder. Circadian rhythm disruption seen in depression has been theorized to contribute to cognitive decline.
Patients with neurodegenerative dementia exhibit a considerably more fast rate of forgetting as differed to depressed and normal people who forget data at a similar rate. Depressed individuals with memory impairment also tend to show less random variation in their responses. A clearcut ‘unified theory’ for the cognitive impairment in depression has not been formulated, but research points to an encoding problem seen in these patients. A depressive disorder is associated with negative automatic thought (NAT) and rumination, which encroach into the consciousness affecting cognition. Lack of natural instincts linked with motivation, impetus, action, concentration, and arousal seems to be associated with the presence of effort mandating cognitive impairment in depressive disorders.
The assessment of depressive symptoms in dementia is confounded by numerous factors: overlapping symptoms, the issue of symptom continuation, communication problems in severe dementia, and reliability of caretaker opinions. A detailed history and a thorough mental status examination are required for adequate diagnosis.
Overlapping symptoms in history are decreased interest in pleasurable activities, altered sleep, decreased/increased appetite, increased/decreased psychomotor activity, difficulty concentrating, and decreased energy. The likelihood of a superimposed depression in neurocognitive dementia should be contemplated when the patient's symptoms such as sleep alterations due to loss of diurnal rhythm, or lack of motivation become more serious over a short span of time. In severe dementia, a history of depressive symptoms may be hard to find secondary to aphasia. In such cases, the collection of history from the caregiver as well as detailed observation during the examination is required to formulate a diagnosis. Besides, sometimes patients with dementia have anosognosia (refusal of disability), which further complicates the reporting of symptoms suggestive of depression.
Collecting history from the caregiver can benefit, as well as complicate the diagnosis as they are themselves vulnerable to increased degrees of responsibility and sadness. The occurrence of depression in dementia has been strongly associated with the caretaker burden and their own depression.
Clues in history which helps to diagnose depression are—
In addition to history, a detailed mental status examination, neurocognitive tests, and laboratory tests are required to rule out other medical causes. Observing the patient's behavior during examination is very critical and important. Depressed people lack adequate motivation to finish the task, take additional time to accomplish the task, and document frequent attention or concentration problems. They are usually apathetic and easily diverted. Patients with depression often document memory difficulties and associated distress repeatedly. On the other hand, patients with dementia seem to be less distressed and familiar with the magnitude of their own cognitive deficiencies.
On further questioning during the mental status examination: Patients with depression either do not respond or will reply," I don't know" to questions pertaining to orientation, attention, concentration, memory, calculation, abstraction, and judgment.
In addition to history and mental status examination, laboratory testing to rule out other medical causes of cognitive deficits such as HIV, syphilis, vitamin B12, and folate deficiency, and paraneoplastic syndromes, etc. should be ordered.
Neuropsychological tests— Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), Wechsler Memory scale (WMS), clock drawing test, and Trail Making test are commonly used. RBANS is a test that measures immediate and delayed memory, attention, language, and visuospatial skills. It was formulated for two primary applications: as a test for the diagnosis and description of dementia and as a tool for finding neurocognitive deficiencies in a mixture of disorders. WMS measures patients' performance on seven domains testing the auditory, visual, visual working, immediate, and delayed memory.
Neuroimaging studies— Magnetic Resonance Imaging (MRI), Positron Emission Tomography (PET), Single Photon Emission Computed Tomography (SPECT) are ordered to look for particular brain abnormalities seen in dementia.
Rating Scales— The most commonly used scale for screening depression in dementia is the Cornell Scale for Depression in Dementia (CSDD). The CSDD is a 19-item instrument assimilating data from both patient and caretaker. It evaluates mood-related signs (Anxiety, sadness, anhedonia, irritability), behavioral disturbance (Agitation, retardation loss of interest), physical signs (Appetite and weight loss), cyclic functions (diurnal variation in symptoms) and ideational disturbance (Suicide, poor self-esteem, etc.). Scores greater than ten are associated with a probable diagnosis of a major depressive episode. Scores of more than 18 indicate a definite major depressive disorder.
The prognosis of depressive cognitive disorders is controversial, with surveys documenting transformation to irreversible neurodegenerative dementia and additional reviews documenting no transformation. In the past, it came to be more obvious that depression correlated with cognitive deficits can be the prodromal phase of dementia. In this respect, current data reports depression to be related to a twofold heightened risk of transforming to irreversible dementia. Researchers have found that over an interval of 4 to 5 years, more than 70% of cases originally diagnosed with depression with cognitive impairment transformed into dementia, and 18% of these cases were originally found to have no changes in cognition.
Depressive cognitive disorders are related to a considerable amount of disability. It complicates management, exacerbates functional problems, and govern other adverse consequences. It is associated with interference with life and activities due to prolonged hospitalization. Cases with coexisting depressive disorder and dementia seem to utilize health care and the nursing home facility at a considerably increased amount than cases with either disorder alone. Caretaker responsibility is heightened many folds when they have to care for patients who have both dementia and a depressive disorder. The additional important complication of the depressive cognitive disorder is the suicidal ideation. The percentage rises in aged separated or divorced white men. Social withdrawal and associated medical illness further enhance the risk. Depression with dementia furthermore increases the likelihood of medical co-morbidity in old age like cardiovascular illnesses, diabetes, stroke, etc.
The heightening number of the elderly population gives rise to an increasing number of old-age mentally ill. Disorders such as dementia and late-onset depression not merely cause difficulties among their sufferers, they diminish the quality of life and inflict a heightened responsibility on the caregiver. Depressive cognitive disorders, neurodegenerative dementia, and late-onset depression contribute to all disability-adjusted life years (DALY) in the senior community. Hence, aging possesses a profound impact on public and health programs. Thus, knowledge about the symptoms and signs of the depressive cognitive disorder is essential for cases and caretakers, which would encourage them to seek timely assistance, and avoid setting their lives at risk.
Depressive cognitive disorder continually poses a diagnostic difficulty. These cases demonstrate symptoms of a major depressive disorder associated with cognitive impairment. It may be due to numerous causes with several etiologies. While the record may illustrate that the person has pseudodementia, the reason is complicated to know without a comprehensive examination, assessing cognition, and ordering laboratory tests.
For the early diagnosis and treatment of depressive cognitive disorders, collective interprofessional activity is meaningful. For example, if an aged person complains of memory problems along with behavioral disturbances, the clinician should contemplate the differential of depressive cognitive disorders. An additional difficulty in old-age is polypharmacy and medication interactions. The pharmacist should frequently monitor the drug dispensing and discuss with the physician if there are any potentially lethal prescriptions. Eventually, a psychiatric nurse and a social worker should be involved in the supervision of these cases as they want assistance services, a stable living atmosphere, and appreciating caretakers. An interprofessional squad strategy is crucial if one wishes to enhance outcomes and decrease undesirable circumstances related to depressive cognitive disorders.
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