The question of what mental disorders actually are is a highly controversial one with a long-running history. Here we provide an initial perspective on this challenging issue.

 Classification systems such as DSM-5 and ICD-11 consider mental disorders as thoughts, feelings or behaviors that cause distress or suffering. These disorders are therefore assessed or ‘diagnosed’ in a clinic according to the presentation of particular constellations of such thoughts, feelings and behaviors – the ‘symptoms’ – that are grouped together under different diagnostic labels. Treatments then aim to alleviate these symptoms through varying means.

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From symptoms to brain

But where do mental disorders actually come from? Because thoughts, feelings and behaviors arise from the brain, it stands to reason that there must be something going on in the brain – a change, dysfunction or pathology maybe – which accompanies these outcomes or ‘symptoms’.

Here one of the main questions revolves around whether mental health disorders or symptoms should be seen as arising when something goes “wrong” in the brain, similar to how neurological and physical diseases are viewed. Therefore, by measuring what’s gone “wrong”, such as by comparing patients against healthy controls, you can reveal the changes in underlying biology and develop new treatment interventions that mitigate these changes, or, at the very least create a pathway to identifying at-risk individuals. This shift in focus from psychological challenges to biological dysfunction in some sectors of clinical research is motivated by advances in neuroscientific understanding, a desire to explore alternative non-DSM frameworks to guide mental health research and treatment development (e.g. RDoC from the NIMH), and a belief that it may help remediate the stigma currently associated with mental health disorders.

To figure this out is a challenging task, however. This is because, as with various disorders or diseases of the body, the same symptom such as fever or headache can reflect a host of different underlying etiologies. Similarly,  mapping aspects of brain physiology to a disorder defined as a loose constellation of symptoms is a messy endeavor, while, on the other hand, the descriptive psychological symptoms that patients present don’t map easily to the more neuroscientific frameworks such as the RDoC.

In addition, the person experiencing these symptoms has a unique genetic, developmental and experiential trajectory that has shaped their brain to operate as it does, generating a life history and a personalized predisposition to certain thoughts, feelings and behaviors that may vary widely across people presenting with the same psychological symptoms. Consequently, biological changes associated with the same “symptoms” or disorder may also differ, to some extent, to reflect these individual differences.

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And of course, the person has a body as well as a head and the physical processes (healthy or otherwise) which are ongoing within their body systems have the capacity to influence what is going on north of their shoulders and so considering this angle can also be important.

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The fact that no reliable biomarker for any mental health disorder has yet been identified, despite considerable research, indicates just how challenging this brain-based approach is.

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From Brain to Environment

The brain is a constantly evolving organ that resculpts itself in response to its trajectory of experience. It is therefore important to recognize that the person experiencing these psychological symptoms isn’t operating in isolation. Every individual lives a life full of people, situations and events which naturally have an ongoing impact on their thoughts, feelings and behaviors, and on the patterns of neural activity inside their brain. And it is also natural for certain life situations to elicit psychologically challenging responses such as sadness, grief and stress.

To what extent, then, is the environment responsible for their symptoms? Just as poor air quality can exacerbate symptoms of asthma to intolerable levels, or elements of diet can exacerbate symptoms of diabetes, so too can elements of the stimulus environment exacerbate mental health symptoms. So how should one account for environment in the equation?

Complex and multi-layered

What’s clear is that mental disorders are in fact multi-layered, multifaceted phenomenon with various complex etiologies. It is therefore not surprising that there are so many different (and often opposing) viewpoints on what mental disorders actually are, how they should be classified, how they should be assessed, and how they should be treated.

And while an exploration of new approaches which go beyond just psychological challenges is clearly warranted, seeing all mental health disorders as brain disorders is still a matter of much debate, especially for disorders (e.g. depression) which can be heavily influenced by socio-environmental factors, and where something in a person’s life situation may have also gone “wrong”.

Another approach is therefore to identify mental health disorders at the level of the person. To see the affected “organ” as the person themselves. A person who has a brain. Who has feelings, thoughts and behaviors. Who has a social, environmental context. Who has a genetic, developmental, experiential trajectory.  And who has a physical body. All of which are interrelated.

In other words, an approach which embraces the multi-layered, multifaceted and heterogeneous nature of mental health disorders, rather than trying to pit one approach against the other.

What is best for patients is best for science.

But regardless of whether you view mental health disorders as being at the level of the mind, the brain or the person, the real answer to the question “what is a mental health disorder”, and the related questions of how they should be diagnosed, assessed and classified, is guided by what ensures the best human outcomes. And ultimately, this comes from a combination of a biological approach that facilitates the development of new pharmacological treatments, a psychological approach that allows the development of new behavioral therapies, and a socio-environmental approach which supports the development of new social policies and life interventions.

 

References:

Banner, N. (2013). Mental disorders are not brain disorders. Journal Of Evaluation In Clinical Practice, 19(3), 509-513. doi: 10.1111/jep.12048

Borsboom, D., Cramer, A., & Kalis, A. (2018). Brain disorders? Not really: Why network structures block reductionism in psychopathology research. Behavioral And Brain Sciences, 42. doi: 10.1017/s0140525x17002266

Frisch, S. (2016). Are Mental Disorders Brain Diseases, and What Does This Mean? A Clinical-Neuropsychological Perspective. Psychopathology, 49(3), 135-142. doi: 10.1159/000447359

Insel, T. (2010). Rethinking Mental Illness. JAMA, 303(19), 1970. doi: 10.1001/jama.2010.555

White, P., Rickards, H., & Zeman, A. (2012). Time to end the distinction between mental and neurological illnesses. BMJ, 344(may24 1), e3454-e3454. doi: 10.1136/bmj.e3454