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Tara Thiagarajan Ph.D.

Your Individual Depression

Depression is a complex spectrum of symptoms that needs a personalized approach.

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According to a recent report by the World Health Organization, 4.4% of the global population suffer from a depressive disorder [1]—this means that about 322 million people are living with depression around the world. It is so common that even if you haven’t personally suffered from it, you probably know someone who has, and have some sense of how terrible it can be. With symptoms like overwhelming sadness, feelings of worthlessness, and mental and physical fatigue, depression can turn your life upside down, put you out of work, break up your marriage and, at its worst, drive someone to suicide.

But depression, despite the fact that it is known by that single label, represents a broad constellation of symptoms. Some people might be anxious and angry while others find themselves withdrawing from society or unable to make decisions. Two depressed people are never the same and shouldn’t be treated as such.

This diversity in symptoms, and the fact that depression is simply a name for a group of symptoms without a corresponding clear understanding of the underlying biology, makes the diagnosis of depression, and the selection of the best treatment pathway, extremely challenging.

Is a questionnaire sufficient for diagnosis?

When there is something physically wrong with your body, doctors usually turn to some kind of laboratory test to screen for disturbances in your internal biology. This allows them to identify possible underlying causes and guides their choice of treatment.

However, when it comes to your brain, it isn’t that simple. There is no straightforward lab test that can tell you whether or not you have depression. And the same applies for most other mental health disorders: Neuroscience doesn’t yet have the answers to what the underlying causes of these "symptom-based" disorders actually are.

Instead, with mental health disorders such as depression, clinicians turn to standardized questionnaires and interviews which allow them to track the experiential nature of an individual's set of symptoms. These are subjective forms of assessment which ask you about the type and number of symptoms you have, how long you’ve had them, and how much they interfere with your ability to live a “normal” life.

In a way, it is not too different from a quiz score in a popular magazine telling you, for example, how emotionally healthy your relationship is.

Many roads to a diagnosis of depression.

As with many surveys of this nature, there are multiple ways to arrive at the same answer. For example, diagnosis of depression based on DSM-5 criteria, a common but often criticized approach for mental health diagnosis, uses a set of 9 symptom criteria and has up to 126 answer combinations which can result in a positive diagnosis [2]. Other screening questionnaires, such as the Hamilton Depression Rating Scale (HAM-D) [3] and Patient Health Questionnaire-9 (PHQ-9) [4], bring ratings of symptom severity into the mix, which further increases the complexity of possible answer combinations. What’s more, different clinical screening questionnaires for depression actually ask about slightly different sets of symptoms, further complicating assessment of an already highly heterogeneous disorder [5].

Translating symptom combinations into treatments.

When a diagnosis of depression can be based on differing schemas of emotional, cognitive, behavioral and physical symptoms, how can you make sure that you, as an individual, are getting the right treatment?

There are a host of potential treatments available for depression, from antidepressant medication to psychotherapy to exercise and cold-water swimming. Working with your doctor to find the best one(s) for you is often a process of trial and error, rather than precision medicine—perhaps not unexpected when you consider the mode of diagnosis and variability of symptom criteria. It is therefore important to understand and track your particular set of symptoms—which can separate you from the symptoms of others, find clarity on which symptoms you are keen to mitigate, and ask your doctor how particular treatments have fared at a symptom level.

Detangling this complexity, both from the perspective of underlying biology and self-reported symptoms, is the mission of many scientists working in the fields of neuroscience and mental health research. Theories such as the chemical imbalance concept abound; however, clear proof is elusive. While the research continues, it is important that if you are suffering from depressive symptoms, you try to build your own understanding of your particular symptom constellation and their triggers, in order to find the best possible course of treatment.


[1] Depression and Other Common Mental Disorders, Global Health Estimates, World Health Organisation (2017)…

[2] Fried, E., & Nesse, R. (2015). Depression is not a consistent syndrome: An investigation of unique symptom patterns in the STAR*D study. Journal Of Affective Disorders, 172, 96-102. doi: 10.1016/j.jad.2014.10.010

[3] Hamilton, M. (1960) A Rating Scale for Depression, Journal of Neurology, Neurosurgery & Psychiatry, 23, 56-62


[5] Fried, E. (2017). The 52 symptoms of major depression: Lack of content overlap among seven common depression scales. Journal Of Affective Disorders, 208, 191-197. doi: 10.1016/j.jad.2016.10.019

About the Author

Tara Thiagarajan, Ph.D., is the Founder and Chief Scientist at Sapien Labs, which researches brain activity and its relation to mental health.