Depression in Neurological Disorders. Introduction
Depression is a complex mental health condition that can manifest in various forms and often co-occurs with other medical conditions.
This essay explores the comorbidity of depression with neurological disorders, emphasizing its prevalence and impact on patients’ overall well-being.
Depression in Alzheimer’s Disease
Depression is a common comorbidity in patients with Alzheimer’s Dementia (AD), with prevalence rates reaching up to 50%. Moreover, research suggests that depression may act as a risk factor for the development of cognitive impairments or dementia later in life.
One potential link between depression and dementia lies in the observation that depression can contribute to hippocampal atrophy. Conversely, depression ranks as the third most common psychiatric symptom in Alzheimer’s Dementia, following apathy and psychotic symptoms. High rates of depression comorbidity also corelates with fronto-temporal dementias and Lewy Body dementia.
The neuropsychological assessment for distinguishing depression from dementia is challenging during the acute phase of depression. Making accurate differential diagnosis is possible first after severe depression subsides. These diagnostic tests are comprehensive, evaluating verbal episodic and non-episodic memory, executive functions, attention, language, visual processing, and processing speed.
Depression in Parkinson’s Disease
In functional imaging studies, depressed patients with Parkinson’s Disease exhibit significantly reduced metabolic activity in limbic areas and the basal ganglia. Similar to Alzheimer’s Disease, prior depressive episodes may elevate the risk of developing Parkinson’s dementia.
It is crucial to exercise caution when selecting antidepressant treatments for these patients, as they often respond with blood pressure and motor side effects.
Huntington’s Chorea and Depression
Depression is also highly prevalent in Huntington’s Chorea, with reported rates of up to 75%.
Depression in Multiple Sclerosis (MS)
Multiple Sclerosis (MS) is frequently comorbid with depression., with a prevalence ranging from 25% to 50% of MS patients suffer of depression. Multiple sclerosis patients often display poor therapy adherence and a high propensity for suicidal ideation. However, also the immunomodulatory medications used in MS treatment also has a depression-triggering effect.
Amyotrophic Lateral Sclerosis (ALS) and Depression
Depression’s occurrence is also frequent in in Amyotrophic Lateral Sclerosis (ALS). The diagnosis of depression in ALS is difficult because of the overlapping symptoms like anorexia, insomnia, or fatigue, occurring independently of depression. Whether the prevalent depression in supranuclear gaze palsy or corticobasal syndrome represents prodromal syndromes remains uncertain.
Vascular Depression (Subcortical Ischemic Depression)
The concept of vascular depression emerged in the late 1990s, defining it as a cerebrovascular condition that predisposes, causes, or sustains depression in older individuals. The late-life depression and cerebrovascular changes are intertwined. The genesis of cerebrovascular depression depends on the extent and distribution of vascular damage of affected networks.
The pathologies in fronto-striatal and fronto-limbic connections also contribute to depression. Clinical presentation primarily includes executive function problems, psychomotor retardation/inhibition, and apathy. Cognitive deficits take centre stage, and affected individuals are often unaware of their illness and exhibit suspicion.
Besides executive dysfunction, these patients may struggle with visual naming difficulties and reduced verbal fluency. There is an increased risk of treatment resistance, incomplete remission, and dementia development.
Imaging changes are detectable as hyperintensities in the subcortical white matter, reflecting the organic basis of vascular depression. The severity of depression often correlates with the extent, location, and volume of these defects, with temporal and frontal lesions most strongly associated with depression.
Depression and Substance Use Disorders
There is a high comorbidity between depression and substance use disorders, especially among older individuals.
Alcohol Use and Depression
Notably, alcohol dependence is significantly higher among older depressed patients compared to non-depressed counterparts. This comorbidity is associated with a high risk of suicide, with around 60% increase compared to depressed individuals without alcohol issues.
Opiat/Opioids Use and Depression
Depression is also common among those with opiat/opioid dependence, often accompanied by anxiety and personality changes. This comorbidity is particularly evident in patients with chronic pain syndromes. Moreover, the number of individuals aged 65 and older who consume opioids doubled in Western countries due to the COVID pandemic and socio-economical changes.
Misuse of Stimulants and Depression
In younger patients, high comorbidity between depression and anxiety correlates with dependence from stimulants such as cocaine, amphetamine and methamphetamine.
Tobacco Dependence and Depression
In the case of nicotine dependence, withdrawal is associated with an increased risk of depression, whereas sustained smoking cessation is linked to a significant reduction in depressive symptoms.
Depression and Personality Changes in Elderly Patients
Research on the comorbidity of depression and personality disorders in older patients is limited. However, some studies have reported prevalence rates as high as 24%. The presence of a personality disorder is often associated with an early onset of depression. Certain personality traits, such as avoidance, dependency, and perfectionism, are considered risk factors for this comorbidity. These traits can lead to greater loss of independence and delayed therapeutic success. On the other hand, positive coping strategies, self-efficacy, and social competence are protective factors.
Depression and Pain
A shared pathogenic basis for depression and pain was postulated in the 1990s. Biogenic amines, serotonin, and norepinephrine appear to play a significant role in the development of comorbid symptoms. The lifetime prevalence of pain in depressive patients averages 65%, with chronic pain, particularly in the head, abdomen, joints, and chest, being strongly associated with depression. This comorbidity is more common among women.
Depression and Neurological Disorders Caused by Cardiovascular Diseases
A close relationship exists between late-life depression and cardiovascular diseases. This connection appears to be reciprocal: cardiovascular events increase the risk of depression, and depression, in turn, acts as a risk factor for cardiovascular diseases. The risk of ischemic heart disease is increased by 1.5 to 2 times in older individuals with depression. Conversely, approximately 20% of patients experience depression following a myocardial infarction, which, in turn, raises mortality rates in these individuals by 3.5 times in the first six months after the event.
Depressive symptoms lead to a worse disease course, frequent hospitalizations, and reduced benefits from cardiovascular surgeries. Various pathophysiological mechanisms are discussed regarding this comorbidity, including an imbalance between sympathetic hyperactivity and parasympathetic underactivity, reduced heart rate variability, changes in the beta-adrenergic system, and overactivity of the hypothalamic-pituitary-adrenal axis.
Depression in Neurological Disorders. Conclusion
Depression frequently co-occurs with neurological disorders, substance use disorders, pain, personality changes and cardiovascular diseases in older individuals.
Recognizing depression in patients with these neurological conditions is crucial for their overall well-being and treatment outcomes.
Healthcare professionals must take a multidisciplinary approach to manage these complex cases. The treatment often requires a multidisciplinary approach involving psychiatrists, neurologists, psychotherapists and social workers. A combination of psychotherapy, pharmacotherapy, and medical interventions must be tailored to the specific needs of the patient.
Despite remarkable successes in treatment of depression associated with neurological disorders, there is further need for research. Only a better understanding of the underlying mechanisms of such comorbidities will facilitate development of more effective treatment methods.