Is a medical illness causing your patient’s depression?
Endocrine, neurologic, infectious, or malignant processes could cause mood symptoms
27 Irritability, discouragement, and a sense of frustration are more common than low self-esteem and guilt.28
Depression may be more prevalent in MS patients with brain lesions compared with those with spinal cord lesions.29 Imaging studies indicate that depressed MS patients are more likely to have hyperintense lesions in the left inferior frontal regions of the brain and greater atrophy of the left anterior temporal region,30 indicating that the disease may play a role in depressive symptoms.
Parkinson’s disease (PD). Nearly one-half of PD patients experience depression, which recent research suggests is related to neuroanatomic degeneration and not a reaction to having the illness.31
Signs and symptoms. Because PD can present with sleep disturbances, bradykinesia, restricted range of facial expression, and apathy, it initially might be mistaken for a depressive disorder.
Other neurologic disorders. Depression in Alzheimer’s disease typically involves prominent anhedonia, irritability, apathy, and anxiety, rather than suicidal ideation and guilt.32 In traumatic brain injury, the most common psychiatric disturbance is a depressive syndrome resembling endogenous depression.32 Progressive supranuclear palsy—a degenerative disorder of the basal ganglia, brainstem, and cerebellar nuclei—is associated with cognitive impairments and personality changes and may present as depression.33
Infectious disease
Human immunodeficiency virus (HIV). Depression affects 22% to 45% of HIV patients, particularly women, homosexual men, intravenous drug users, and patients with a history of depression.34 The cause of depression in HIV infection is unclear because studies are complicated by factors such as:
- social stigma and isolation associated with HIV
- side effects (such as fatigue) of antiretroviral medications
- comorbid opportunistic CNS infections, such as tuberculosis or cryptococcal meningitis
- the virus itself, which is known to affect the brain.35
Certain sociodemographic factors are associated with depression in HIV patients, but Gibbie et al36 found that CD4 count and viral load are not. This suggests that HIV does not directly cause depression, although research is ongoing. Comorbid substance dependence and AIDS-related dementia can complicate the clinical picture.
The depressive syndrome in patients with HIV typically does not precede the diagnosis of HIV. Diagnosing depression in HIV patients—regardless of the cause—is crucial because of its effect on quality of life, productivity, medication adherence, and mortality.37
West Nile virus. Among the one-third of patients who report new-onset depression after West Nile infection, 75% experience mild-to-severe depression as measured on a depression scale.38 Studies of depression in West Nile virus infection are complicated by recall bias, illness-related disability, and fatigue that interferes with psychiatric assessment. Similar to HIV, a depression diagnosis typically is made following a known West Nile virus infection.
Lyme disease. More than one-third of patients diagnosed with post-Lyme syndrome—chronic symptoms that persist after antibiotic treatment—will have depression during their lifetime.39 One report that attempted to determine a causal relationship between Lyme disease and depression found a similar lifetime incidence of depression in those with Lyme disease and in the general population. Even so, the incidence of depression doubled in this sample after the onset of Lyme disease. Studies of this relationship are confounded by other effects of Lyme disease, small numbers of subjects, and recall bias.
Signs and symptoms. Exposure to ticks, cranial nerve involvement, arthralgias, memory deficits, and psychotic depression may suggest Lyme disease.
Creutzfeldt-Jakob disease is a rare prion disease that can be genetic, spontaneous, or acquired via contaminated beef, corneal transplants, or dural transplants. Patients may present with cognitive impairment, fatigue, emotional lability, and depression.
Signs and symptoms include changes in the brain seen on an MRI, rapid physical and mental decline, and myoclonus and ataxia signs that occur late in the disease. Depression caused by this incurable disease often fails to respond to treatment.
Neurosyphilis patients may experience personality changes, irritability, psychosis, and decreased self-care, which may be interpreted as anhedonia or depressed mood.
Signs and symptoms. Common physical signs include dysarthria, hyperreflexia, cognitive decline, hallucinations, tremor, tabes dorsalis, and Argyll Robertson pupils. Neurosyphilis is confirmed by positive venereal disease research laboratory test of cerebrospinal fluid and treated with high-dose penicillin. Consensus is lacking on the role of psychotropic medications for the management of psychiatric symptoms.40
Hepatitis C patients have a higher lifetime prevalence of major depression compared with controls.41 Although evidence does not support a causal link between hepatitis C infection and depression, anecdotal reports persist.42 Studies of comorbid depression and hepatitis C are complicated by hepatic encephalopathy, fatigue, medication side effects, and social and economic factors associated with hepatitis C. Physical symptoms include decreased appetite, fatigue, fever, nausea, vomiting, abdominal pain, clay-colored stool, joint pain, and jaundice.
