Medical expert of the article
New publications
Depressive Disorder - Diagnosis
Last reviewed: 04.07.2025
All iLive content is medically reviewed or fact checked to ensure as much factual accuracy as possible.
We have strict sourcing guidelines and only link to reputable media sites, academic research institutions and, whenever possible, medically peer reviewed studies. Note that the numbers in parentheses ([1], [2], etc.) are clickable links to these studies.
If you feel that any of our content is inaccurate, out-of-date, or otherwise questionable, please select it and press Ctrl + Enter.
The diagnosis of depressive disorder is based on the identification of the symptoms and signs described above. There are a number of short screening questionnaires. They help in identifying some depressive symptoms, but cannot be used in isolation to establish a diagnosis. Specific closed questions help in identifying the patient's symptoms required by the DSM-IV criteria for a diagnosis of major depression.
The severity of the condition is determined by the degree of suffering and impairment of functioning (physical, social, and professional), as well as the duration of symptoms. The presence of suicidal risk (manifested in suicidal thoughts, plans, or attempts) indicates the severity of the disorder. The physician should gently but directly ask the patient about thoughts and intentions to harm themselves or others. Psychosis and catatonia indicate the severity of depression. Melancholic symptoms indicate severe or moderate depression. Concurrent somatic problems, substance abuse, and anxiety disorders may worsen the condition.
There are no laboratory tests that are pathognomonic for depressive disorders. Tests for limbic-diencephalic dysfunction are rarely revealing or helpful. These include the thyrotropin-releasing hormone stimulation test, the dexamethasone suppression test, and sleep EEG to assess rapid eye movement latency, which is sometimes abnormal in depressive disorders. The sensitivity of these tests is low; the specificity is somewhat better. Positron emission scanning may show decreased cerebral glucose metabolism in the posterior frontal lobes and increased metabolism in the amygdala, cingulate gyrus, and infrageniculate cortex (all moderators of anxiety); these changes normalize with successful treatment.
Laboratory tests are necessary to rule out somatic conditions that may be the cause of depression. Necessary tests include a complete blood count, thyroid-stimulating hormone levels, electrolytes, vitamin B12 , folates. Sometimes toxicology tests are necessary to rule out the use of psychoactive substances.
Depressive disorders should be distinguished from demoralization. Other mental disorders (e.g. anxiety disorders) may mimic or mask depression. Sometimes more than one disorder is present.
Major depression (unipolar disorder) should be distinguished from bipolar disorder.
In older patients, depression may manifest as "dementia" depression (previously called pseudodementia), which causes many of the symptoms and signs characteristic of dementia - psychomotor retardation and poor concentration. However, early dementia can provoke the development of depression. Therefore, if the diagnosis is unclear, it is necessary to treat depressive disorder.
Differentiating between chronic depressive disorders such as dysthymia and substance use disorders can be challenging because they can coexist and exacerbate each other.
It is also necessary to exclude somatic diseases that can cause depressive symptoms. Hypothyroidism often causes symptoms of depression and is quite common, especially in the elderly. Parkinson's disease can manifest with symptoms that mimic depression (i.e. loss of energy, lack of expression, low motor activity). A thorough neurological examination is necessary to exclude this disorder.
[