It’s normal to experience periods of sadness and low mood. We can feel ‘down’ in response to stress, difficult personal events, or for physical reasons such as a lack of sleep, exercise, or nutritious food.

Often this low mood lifts on its own; sometimes we can lift it by making small changes, such as resolving a difficult situation, getting more sleep, or talking things through with a friend.

However, persistent low mood could be a sign of clinical depression. If the negative feelings:Dunn, K. (2016). Understanding Depression. [online] London: Mind. Available at: [accessed 28 Sept. 2017].NHS Choices. (2016). ‘Clinical depression’. [online]. Available at: [accessed 28 Sept. 2017].

  • Don’t lift within a few weeks
  • Become too overwhelming
  • Are stopping us from carrying on with life as normal

Then it’s important to get to the bottom of what might be contributing to this depression, and identify its root cause. See possible contributors to depression on this page to ascertain which ones might be affecting you.

Some long-term health conditions, such as cancer, heart disease, and diabetes can also cause depression, as can certain types of medication, such as beta-blockers, stimulants, and anticonvulsants.

Symptoms of depression

Depression affects everyone differently, and its symptoms can vary widely. It affects the whole body, and can include the following symptoms in various combinations:Chopra, D. and Tanzi, R. (2013). Super Brain. London: Rider, pp. 61-73.

Mental symptoms

  • Persistent sadness
  • Hopelessness
  • Anxiety
  • Guilt
  • Low levels of motivation
  • Feeling empty and numb
  • Lacking confidence and self-esteem
  • Difficulty expressing feelings (especially those above)
  • Irritability
  • Memory problems
  • Poor concentration
  • Lack of interest in activities previously enjoyed
  • Finding it hard to spend time with other people
  • Feeling disconnected in social situations

Physical symptoms

  • Changes in appetite
  • Changes in sex drive
  • Difficulty falling or staying asleep, or sleeping too much
  • Decreased energy
  • Feeling agitated and restless
  • Aches and pains with no obvious physical cause
  • Exhaustion, which seems to be chronic

Different types of depression

Depression can range from mild to severe, and its severity can change from day to day, week to week, and month to month.

There are also some specific types of depression, although you do not have to fit into any of these particular categories to be diagnosed with depression:

Chronic depression is continuous mild depression that lasts for two years or more. It is also known as ‘dysthymia’ or ‘persistent depressive disorder’.

Bipolar depression is depression with dramatic changes in mood: it can vary between two ‘poles’, an extreme high (mania, or hypomania) and an extreme low (depression).

Prenatal Depression/Postnatal Depression (PND). This is depression during pregnancy (prenatal) or after the baby is born (postnatal), which is usually linked to hormonal imbalances.

Seasonal Affective Disorder (SAD). A depression that usually occurs during the winter months and is often linked to a lack of natural light.

Diagnosing depression

Depression is most often diagnosed through a simple question-and-answer session with your doctor.

There are a variety of semi-structured interviews, rating scales or other questionnaires that they can use. The most common are:

  • The most common of the scales
  • Filled in by the doctor
  • 17 or 21 items, both physical and psychological, from suicidal thoughts and hopelessness to reduced libido and weight loss
  • Scored between 0 and 4 points

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  • Another common scale filled in by the doctor
  • 10 items, including sleep, appetite, concentration, and sadness (reported and apparent)
  • Scored between 0 and 6 points

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  • One of the most common questionnaires filled in by the patient themselves
  • 21 multiple-choice questions
  • Scored between 1 and 40 points

Click here for more information.

Lab tests

There is currently no biological test that can diagnose depression with certainty, because its particular biomarkers – measurable indicators of bodily processes – haven’t yet been identified. Research into these biomarkers is still in its infancy, though it’s expanding rapidly.

In integrative and functional medicine, however, biochemical tests and imaging are often conducted to diagnose biochemical imbalances that could be causing mental health symptoms, such as hormone imbalances, gut issues, toxicity, or nutritional imbalances.

Tests that are used in functional and integrative medicine include:

Doctors can check our blood for levels of various hormones and other chemicals: these tests include hormone panels, nutritional status panels, and toxicology screens.

There has been some success in developing a blood test which looks for markers of inflammation, and Inflammation is increasingly being recognized as a substantial contributor to depression and other mental health issues.

This test can also help to show which type of antidepressants might work best for each individual.Roberts, M. (2016). ‘New blood test targets depression’. [online] BBC News. Available at: [accessed 27 Sept. 2017]. 


Stool tests can help to identify pathological bacteria and parasites that might be causing gut dysbiosis, and can also test for Leaky gut (damage to the gut lining).

Urine tests such as an organic acid test can help to identify bacteria, parasites, and yeasts, and test for nutritional imbalances, toxicity, and hormonal imbalances.


By regularly measuring the levels of hormones in our saliva, doctors can check for imbalances, which can cause mental health symptoms. Saliva tests are especially helpful to measure stress hormone imbalances.

A single-photon emission computerised tomography (SPECT) scan is a type of nuclear imaging test, which means it uses a radioactive substance and a special camera to create 3D pictures of the brain.

SPECT scans can measure blood-flow through different parts of the brain, and thus distinguish between depression and other cognitive issues.

This technology is often used to help doctors prescribe the correct medication.Henderson, T. (2016). ‘What neuroimaging can teach us about depression’. [online] PsychiatryAdvisor. Available at: [accessed 25 Oct. 2017].

An electroencephalogram (EEG) is a test that detects electrical activity in your brain, by attaching electrodes (small, flat metal discs) to the scalp.

It can’t be used to diagnose depression, because the EEGs of depressed people are all different, but there is a relationship between certain variations in EEG patterns and the patients’ response to medications.

By comparing a patient’s EEG to thousands of others in a database (this is the ‘referenced’ part of ‘referenced-EEG’), a psychiatrist can prescribe the medication that is, on past evidence, most likely to work.Greenblatt, J. (2016). Breakthrough Depression Solution. 2nd ed. Forest Lake: Sunrise River Press, p. 73.