Unlike several health conditions, Depression cannot be diagnosed through a laboratory test or any other medical examination.

Instead, doctors make a diagnosis by asking an individual a series of questions regarding their feelings and behaviour – and using various questionnaires wherever possible. It should be noted, sometimes medical tests can be conducted to rule out other causes for symptoms.

A diagnosis of Depression will normally involve a form of talking therapy

What is Depression?

Depression is a serious illness which can have a profound impact on the day-to-day life of someone who suffers from the illness. While the majority of people go through periods of feeling down or unhappy, those who are depressed feel persistently sad or have a low mood for weeks, or perhaps even months. Depression can make life appear pointless, and often leads to suicidal ideation. Depression is a common mental illness, and is usually classed as either mild, moderate or severe. Clinical Depression is the most common form, though there are a range of types, including Postpartum depression and Seasonal Affective depression. The good news is that unlike many mental health conditions, with the right treatment, support and lifestyle, many people with depression will gain full remission.


The symptoms of Depression and other mental illnesses are unique to each individual. Therefore, a doctor will ask the patient a range of questions regarding their symptoms – such as how often depressive phases occur, patterns of thought, possible causes and anything else relevant to the illness.

They will also want to know when these symptoms started, any drug or substance abuse, and whether or not there is a family history of mental illness. It is crucial that in order to receive an accurate diagnosis that the patient answers each question truthfully.

By getting a full picture of how depression affects an individual, a doctor can tailor a treatment plan to fit the specific symptoms.

Diagnostic Criteria

In terms of the actual symptoms, for Clinical Depression (the most common form of depression) to be diagnosed, a patient will generally show at least five of the following symptoms:

  • Depressed mood for the majority of the day, over the course of a few weeks.
  • Loss of interest and enjoyment in formally-enjoyable activities
  • Increase or decrease in appetite and subsequent weight gain/loss.
  • Problems sleeping.
  • General fatigue or lack of energy.
  • Feelings of guilt or worthlessness.
  • Poor concentration, difficulty in decision-making.
  • Lethargy or the feeling of being slowed down, as noticed by those around you.
  • Thoughts of self-harm and/or suicidal ideation.

Sometimes, a blood test or physical examination may be conducted if the doctor believes another illness e.g. Hypothyroidism is causing the symptoms.

Whether or not the depression is regarded as mild, moderate or severe depends on the severity of the symptoms and the subsequent impact they are having.

Often, the Patient Health Questionnaire – commonly known as the PHQ-9 – will be used to measure the severity of depression. The PHQ-9 is a questionnaire which requires the patient to assess their own depression, answering several questions based on their symptoms.


The sooner an individual seeks help for depression, the better. Treatment can certainly help, and in many cases will lead to recovery.

All discussions with a doctor are confidential – unless a doctor believes there is a significant risk to the patient or someone else. Getting a diagnosis can be an important step on the way to recovery.

See Also


This website should be used purely for informational purposes, and does not intend to, nor should it ever, be used as a replacement for professional medical advice.

We strive to keep all of our pages updated, and ensure that our website is full of factual and in-depth information. However, we encourage you to browse this website with care.

As a reminder, this website and all content within it cannot and should not replace the advice of a trained medical professional. You can read our full disclaimer at this link.


If you are struggling with your mental health, help is available. With the right support and treatment, you can make a recovery. For information on helplines, or if you are in a state of crisis, please visit our crisis page by clicking on the relevant link for your geographical location (United Kingdom), (United States), (International). You can also see how to get mental health treatment and the process involved by clicking this link.