Knowing Neurons
Mental HealthNeurological and Psychiatric Disorders

Depression: A disease, a spectrum, or a state of consciousness?

By Darsol Seok

In recent years, conversations about depression and mental health have become more prevalent. For instance, failing an exam or enduring a tough work week might prompt someone to say, “I’m feeling depressed.” But what is depression? Is it a disease or a condition that someone is diagnosed with? Is it a continuous spectrum that everyone experiences? Or is it, as some recent researchers have proposed, an alternative state of consciousness, like dreaming?

Understanding Depression: From the Past to the Present

Historically, depression was not always understood in the context of mental health. Ancient physicians like Hippocrates viewed depression as a biological imbalance of bodily fluids, or humors (Telles-Correia & Marques, 2015). Over the centuries, societal views fluctuated, seeing depression at times as a sign of demonic possession, a moral failing, or a lack of willpower. It wasn’t until the 20th century that a more scientific understanding began to take shape.

Historically, depression was not always understood in the context of mental health.

Today, depression is defined by the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), a publication by the American Psychiatric Association, as a disorder characterized by a constellation of symptoms. These include a depressed mood most of the day, diminished interest in activities, significant weight loss or gain, insomnia or excessive sleeping, fatigue, feelings of worthlessness or excessive guilt, diminished ability to think or concentrate, and recurrent thoughts of death (American Psychiatric Association, 2013). To meet the DSM criteria for clinical depression, these symptoms must persist for at least two weeks and represent a change from previous functioning. This perspective primarily views depression as a disease, under what is called the “medical model of mental illness”: each symptom is a sign of a single, underlying condition (Huda, 2021). 

Rethinking Depression: A Set of Spectrums Rather Than a Single Condition

While the DSM considers all individuals with depression as having the same condition, depression takes many different forms and presentations. To receive a diagnosis of depression under the DSM criteria, an individual must present with at least 5 out of a list of 9 symptoms – this means there are 256 unique combinations of symptoms that could lead to a diagnosis! This broad definition of depression contributes to significant heterogeneity within the diagnosis category, meaning that there are likely multiple subtypes of depression under the DSM’s definition. This has negative consequences for treatment: roughly 50% of patients with depression fail to respond to their first treatment (Corey-Lisle et al., 2004), and nearly all patients treated for depression are prescribed the same type of medication, regardless of their specific symptom presentation (Simon & Perlis, 2010). 

… the National Institute of Mental Health (NIMH) initiated a research approach known as the Research Domain Criteria (RDoC)… This view claims that every individual exists somewhere on multiple dimensions of cognitive, emotional and behavioral functioning

To address this limitation, the National Institute of Mental Health (NIMH) initiated a research approach known as the Research Domain Criteria (RDoC) in 2008 to delve deeper (Insel et al., 2010). This framework posits that all mental disorders represent disruptions in one or more dimensions of functioning. This view claims that every individual exists somewhere on multiple dimensions of cognitive, emotional and behavioral functioning, rather than in discrete categories like “depressed” and “not depressed” (Krueger & DeYoung, 2016). The RDoC approach integrates genetics, neuroscience, and behavioral science to better understand the complexity of mental health. It proposes to do this through a hierarchical framework: genes encode proteins, which affect cellular and neural development, which influence neural structures and functions, which lead to the behavioral and psychological manifestations of mental illnesses. While RDoC is a major organizing principle of modern neuropsychiatric research today, its impact on current treatment of depression still largely remains to be realized. The hierarchical approach to understanding psychiatric disorders is useful for guiding research, but it may still be several years before this approach results in new drugs and treatment stratification strategies.

Network Theory: Depression as a dynamic process

One of the cutting-edge perspectives in understanding depression is the network theory of psychopathology (Cramer et al., 2010; Borsboom & Cramer, 2013). This theory suggests that depression arises from complex interactions within networks of psychological and behavioral factors. Symptoms such as insomnia might exacerbate a person’s risk for other symptoms like fatigue, which in turn can increase feelings of sadness or worthlessness. Thus, rather than seeing depression as stemming from a single cause, network theory views it as a self-organizing network of symptoms influencing and reinforcing each other. Under the network perspective, the “symptoms” of depression make up the essence of depression; together, they constitute depression itself, rather than existing as manifestations of an underlying condition. Individuals prone to depression may have stronger interrelationships between their symptoms, resulting in cycles of depressive symptoms that are challenging to escape without treatment (Pe et al., 2015). 

Depression as an Altered State of Consciousness?

depression might be best characterized as an altered state of consciousness

A recent perspective suggests that depression might be best characterized as an altered state of consciousness, just as dreaming is an alternative state of consciousness to normal, waking life (Whiteley, 2021). Different states of consciousness are defined as global changes in individuals’ perception, cognition, and subjective experience of the world. This perspective suggests that depression is best understood as a different state of consciousness to non-depressed life, given its significant changes in one’s perception of the world, oneself, and the future. People experiencing depression often report feeling as though they are living in a different reality, marked by a pervasive sense of hopelessness that affects their cognitive functions and emotional responses (Ratcliffe, 2015). By positing depression as an alteration in consciousness, this perspective could direct researchers towards examining more global aspects of neural and psychological functioning when studying depression. Like RDoC, while this new perspective may not result in immediate changes in mental healthcare, directing researchers to examine more global changes in neural and psychological functioning could result in novel breakthroughs, helping scientists understand the biological and psychological etiology of depression and paving the way for the development of more effective therapies.

Conclusion

Today, our understanding of depression is the result of centuries of evolution in thought and research. Understanding depression as a complex, multi-faceted condition has significant implications for both research and treatment. For researchers, these multiple perspectives can suggest novel approaches for studying depression under different lenses. For clinicians, a deeper grasp of depression’s diverse manifestations can lead to more personalized and effective treatment strategies. As research continues to unfold, our perception of depression and our strategies to combat it will likely continue to evolve, offering new insights and more refined approaches to mental health research and care.

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Written by Darsol Seok
Illustrated by Divi Bhaireddy
Edited by Alli Lindquist, Keionna Newton, and Shiri Spitz Siddiqi

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References

American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.). https://doi.org/10.1176/appi.books.9780890425596

Borsboom, D., & Cramer, A. O. J. (2013). Network analysis: An integrative approach to the structure of psychopathology. Annual Review of Clinical Psychology, 9(1), 91–121. https://doi.org/10.1146/annurev-clinpsy-050212-185608

Cramer, A. O., Waldorp, L. J., Van Der Maas, H. L., & Borsboom, D. (2010). Comorbidity: A network perspective. Behavioral and brain sciences, 33(2-3), 137-150.

Corey-Lisle, P. K., Nash, R., Stang, P., & Swindle, R. (2004). Response, partial response, and nonresponse in primary care treatment of depression. Archives of internal medicine, 164(11), 1197-1204.

Huda, A. S. (2021). The medical model and its application in mental health. International Review of Psychiatry, 33(5), 463–470. https://doi.org/10.1080/09540261.2020.1845125 

Insel, T., Cuthbert, B., Garvey, M., Heinssen, R., Pine, D. S., Quinn, K., Sanislow, C., & Wang, P. (2010). Research Domain Criteria (RDoC): Toward a new classification framework for research on mental disorders. American Journal of Psychiatry, 167(7), 748–751. https://doi.org/10.1176/appi.ajp.2010.09091379 

Krueger, R. F., & DeYoung, C. G. (2016). The RDoC initiative and the structure of psychopathology. Psychophysiology, 53(3), 351–354. https://doi.org/10.1111/psyp.12551

Pe, M. L., Kircanski, K., Thompson, R. J., Bringmann, L. F., Tuerlinckx, F., Mestdagh, M., Mata, J., Jaeggi, S. M., Buschkuehl, M., Jonides, J., Kuppens, P., & Gotlib, I. H. (2015). Emotion-Network Density in Major Depressive Disorder. Clinical Psychological Science, 3(2), 292–300. https://doi.org/10.1177/2167702614540645 

Ratcliffe, M. (2014). Experiences of depression: A study in phenomenology. OUP Oxford.

Simon, G. E., & Perlis, R. H. (2010). Personalized medicine for depression: can we match patients with treatments?. American Journal of Psychiatry, 167(12), 1445-1455.

Telles-Correia, D., & Marques, J. G. (2015). Melancholia before the twentieth century: fear and sorrow or partial insanity?. Frontiers in psychology, 6, 120118.

Whiteley, C. M. K. (2021). Depression as a disorder of consciousness. The British Journal for the Philosophy of Science. https://doi.org/10.1086/716838 

Author

  • Darsol Seok

    Darsol is a Neuroscience PhD student at UCLA. His research focuses on the use of smartphone and wearable technology to infer subjective states and mental health conditions like depression and anxiety. To do so, he uses a variety of analytical approaches including machine learning, deep learning and traditional biostatistical methods. Previously, he conducted neuroimaging and decision-making research at the University of Pennsylvania, where he completed his Bachelor's. When he's not in lab, Darsol likes to go on runs, watch movies, check out art museums and attend concerts.

Darsol Seok

Darsol is a Neuroscience PhD student at UCLA. His research focuses on the use of smartphone and wearable technology to infer subjective states and mental health conditions like depression and anxiety. To do so, he uses a variety of analytical approaches including machine learning, deep learning and traditional biostatistical methods. Previously, he conducted neuroimaging and decision-making research at the University of Pennsylvania, where he completed his Bachelor's. When he's not in lab, Darsol likes to go on runs, watch movies, check out art museums and attend concerts.

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