There is no test, which will specifically diagnose depression and pinpoint this condition. Diagnosis of depression is a complex procedure, which involves history taking, studying the symptoms, physical examination, lab tests, imaging procedures, and more.

When you go to your doctor with some of the symptoms that are associated with depression, you have made that decision because these symptoms have interfered with your daily tasks.

You should see a doctor if such a thing happens and also if your sadness and a feeling of lowness lasts most time of the day for 15 days or more. Occasional periods of feeling low do not classify as depression.

The doctor then sets about diagnosing depression, which he suspects from your history and a physical examination.

The sooner your depression is diagnosed and the sooner you should seek treatment, the prognosis improves and your cure is faster. Delay can cause complications that can lead to suicidal tendencies

History taking  

There are no specific laboratory tests for blood or radiology to diagnose depression. Diagnosis is based on the following.

  • Your doctor will take a detailed history of your symptoms and identify them with those of depression.
  • History will also include looking for the presence of any existing disease or any medication being taken, which can be the cause of depression. Prolonged use of certain drugs is also associated with depression. Such drugs include steroids, amphetamines, and appetite suppressants.
  • The doctor will look for a history of alcohol abuse, tobacco use, or drug abuse. Alcohol can worsen your depression.
  • He will ask about any history in your family of any mental condition.

The doctor will conduct a physical examination, which involves a routine checkup of the pulse, blood pressure, and temperature. He will examine the lungs for breathing sounds and the heart for heartbeats with a stethoscope.

Screening for depression

Because of the fact that depression is quite common and often goes undetected, you may be asked to fill out a questionnaire, which gives the doctor an in-depth study of your condition.

The two classifications of mental illness commonly used are:

  • Diagnostic and Statistical Manual of Mental Disorders. This is published by the American Psychiatrist Association and is based on all known recorded symptoms of a particular mental disorder. Your answers to the questions will help the doctor to identify the mental condition.
  • International Classification of Diseases. World Health Organization (WHO) has developed this classification and is a much wider system, which covers all diseases and not just mental conditions. The questions are similar and are based on the various symptoms of diseases known.

They may include questions about the presence or absence of motivation, feeling fatigued, sleeping patterns, suicidal thoughts, or a feeling of hopelessness. They may also ask about the frequency and duration of these symptoms.

Using any one of these systems, the doctor can diagnose your depression and the type of depression that is present and also rule out other mental conditions.

Insurance companies also use these systems to reimburse the treatment cost. Such discussions are treated with strict confidence and the family members are told only if the doctor feels that there is a risk of harm to the patient or family members.

Lab tests for diagnosing depression

The doctor will ask for some blood tests and urine analysis to rule out other conditions that have similar symptoms.

  • A complete blood count and ESR are done to rule out any systemic infection or chronic disease.
  • Certain specific tests for thyroid, such as TSH and thyroxine are done to rule out hypothyroidism. This is the most common medical reason associated with feeling depressed.
  • Basic serum electrolytes and serum calcium are done to rule out a metabolic disturbance
  • Testosterone levels are checked in males to rule out hypogonadism (which can be a cause of depression).
  • Cognitive testing and brain imaging are done in the elderly to rule out dementia and Alzheimer’s disease.
  • Tests for chronic diseases are performed to rule them out, such as diabetes, kidney disease, arthritis, HIV/AIDS, cancer, and more.
  • Vitamin D estimation may be done to rule out its deficiency

Other tests used to diagnose depression

Some other tests are done not to pinpoint depression but to rule out conditions, which can be associated with causes of depression.

  • CT scan or MRI or encephalogram (EEG) of the brain to rule out any brain pathology such as a brain tumor.
  • Electrocardiogram (ECG) is done to check for the presence of a heart condition.

Once the diagnosis confirms depression by history, symptoms, and tests, appropriate treatment is started, which can lead to its cure.