by Dorsa Rafiei

Graphic design by Emily Kate Tjan

What if a picture of your brain could tell you the exact state of your mental health? While some scientists and psychiatrists argue that neuroimaging has the power to do just that, other professionals, including the American Psychiatric Association (APA), disagree.¹ 

The dawn of neuroimaging techniques that allow for the assessment of the structural anatomy and functional activity of the brain has lent a significant helping hand in the study and detection of brain disorders. For example, computed tomography scans can identify various neurological disorders, such as cancerous tumours, brain haemorrhages, and head injuries.² In Alzheimer’s disease, magnetic resonance imaging and positron emission tomography can be used in the diagnostic process to assess brain atrophy and beta-amyloid plaque formation, respectively.³ However, while there have been significant advances in the use of neuroimaging for diagnostic purposes, there remain a number of limitations to applying this approach within psychiatry. 

In medicine, it is typical to look at the organ of concern during the diagnostic process. For instance, x-rays are used to visualize broken bones, ultrasounds are used to visualize abdominal organs, and so on. Psychiatry is the one medical field where the organ of concern, the brain, is rarely ever looked at prior to treatment. There are significant gaps in medical literature with regards to psychiatric disorders in general. In fact, medications are often prescribed without knowing the true cause of the psychiatric illness. The current gold standard for making a clinical diagnosis is using the Diagnostic and Statistical Manual for Mental Disorders, 5th edition (DSM-5), which relies on behavioural presentation to make psychiatric diagnoses.⁴ However, the DSM-5 comes with its own limitations, namely low thresholds for diagnosis that may lead to inappropriately classifying certain behaviours as disorders and thereby overdiagnosis (or even misdiagnosis) and overtreatment.^5,6,7

There are currently no laboratory tests for psychiatric disorders in the same way that a blood test or biopsy could determine the presence of thyroid dysfunction or cancerous cells, respectively. The aim of using neuroimaging as a diagnostic tool is to objectively identify psychiatric disorders via biomarkers. The idea is that, once a biomarker is established for a certain illness, neuroimaging can be used to detect said biomarker to aid in the diagnosis of the illness. 

At the forefront of the movement to use neuroimaging as a diagnostic tool in psychiatry is Dr. Daniel Amen, MD, who has become well-known for his forward-thinking approach to diagnosing psychiatric disorders using single photon emission computed tomography (SPECT), which measures blood flow in various parts of the brain and is conventionally used for neurological disorders. Amen claims to be able to use SPECT to diagnose distinct subtypes of attention deficit hyperactivity disorder and to even identify Alzheimer’s in the brain years before symptom onset.^8,9 He also performs SPECT scans before and after treatment to assess its effectiveness. The International Society of Applied Neuroimaging, who believe that functional neuroimaging provides valuable insights into patient diagnosis, support Amen’s work.¹⁰

However, Amen’s approach has been deemed controversial, unethical, and lacking scientific validity by his academic peers. In fact, his work has been compared to modern-day phrenology.¹¹

Research studies have found reproducible neural differences between diagnostic groups; for example, hippocampal atrophy has been commonly observed in depression and enlarged ventricles have been commonly observed in schizophrenia.^12,13 However, these studies may still not be enough to conclude that neuroimaging can diagnose psychiatric illness. Why? Because these research studies depict deviations between groups of patients, not deviations between individual patients. This raises the issue of generalizability because of individual differences in age, sex, medication, comorbid psychiatric disorders, and stage of illness. Therefore, what may be true for most individuals with a disorder may not be true for all individuals with a disorder. Psychiatric disorders are heterogeneous in nature, which makes diagnosis and treatment all the more difficult. In the context of neuroimaging for diagnosis, mental illness can present differently at the neural level between individuals with the same illness.

There are several other factors to consider when asking the question of whether neuroimaging is capable of diagnosing psychiatric disorders. First, it is important to note that existing studies demonstrate correlational, not causal, relationships. That is, an abnormality in a certain brain region does not cause the psychiatric disorder per se, but rather the brain abnormality and the psychiatric disorder co-occur. Second, several disorders may show similar brain abnormalities. Third, psychiatric disorders are not solely caused by observable brain abnormalities; rather, psychiatric disorders are best viewed through the lens of the biopsychosocial model that takes into account biological, psychological, and sociocultural factors. All of the factors discussed above limit the validity of neuroimaging as a diagnostic tool. In fact, the APA has maintained that “neuroimaging has yet to have a significant impact on the diagnosis or treatment of individual patients in clinical settings” and that “at this time, the majority of neuroimaging’s utility remains as a research tool only.”¹

Even though it is said that a picture is worth a thousand words, this logic may not apply to brain scans in psychiatry—at this point in time. Neuroimaging techniques have contributed a great deal to our understanding of the brain and its related disorders. While these contributions have promise, current neuroimaging technology lacks the sensitivity and specificity to reliably diagnose psychiatric disorders. Much advancement in neuroimaging technology is needed in order to confidently rely on its ability to single handedly diagnose such disorders.

References

1. Botteron K, Carter C, Castellanos FX, et al. Consensus Report of the APA Work Group on Neuroimaging Markers of Psychiatric Disorders. Arlington, VA: American Psychiatric Association; 2012.
2. Computed Tomography (CT) SCAN [Internet]. Johns Hopkins Medicine. 2021 [cited 2022May21]. Available from: https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/computed-tomography-ct-scan#:~:text=CT%20scans%20may%20be%20performed,a%20tissue%20or%20fluid%20biopsy.
3. Gazzaniga M, Irvy RB, Mangun GR. Cognitive Neuroscience: The Biology of the Mind, Fifth Edition. W. W. Norton & Company; 2019.
4. Diagnostic and Statistical Manual of Mental Disorders: DSM-5. Arlington, VA: American Psychiatric Association; 2013.  
5. Wakefield JC. Diagnostic issues and controversies in DSM-5: Return of the false positives problem. Annual Review of Clinical Psychology. 2016;12(1):105–32. https://doi.org/10.1146/annurev-clinpsy-032814-112800 
6. Thombs B, Turner KA, Shrier I. Defining and evaluating overdiagnosis in Mental Health: A Meta-Research Review. Psychotherapy and Psychosomatics. 2019;88(4):193–202. https://doi.org/10.1159/000501647
7. Raskin JD, Gayle MC. DSM-5: Do psychologists really want an alternative? Journal of Humanistic Psychology. 2016;56(5):439–56. https://doi.org/10.1177/0022167815577897 
8. Attention deficit disorder (ADD/ADHD) [Internet]. ADD & ADHD Treatment | Attention Deficit Disorder Therapy | Dr. Amen. [cited 2022May15]. Available from: https://www.amenclinics.com/conditions/adhd-add/ 
9. Burton R. Brain scam [Internet]. Salon. Salon.com; 2011 [cited 2022May15]. Available from: https://www.salon.com/2008/05/12/daniel_amen/ 
10. Henderson TA, van Lierop MJ, McLean M, et al. Functional neuroimaging in psychiatry—aiding in diagnosis and guiding treatment. What the American Psychiatric Association Does Not Know. Frontiers in Psychiatry. 2020;11.  
11. Tucker N. Daniel Amen is the most popular psychiatrist in America. to most researchers and scientists, that’s a very bad thing. [Internet]. The Washington Post. WP Company; 2012 [cited 2022May15]. Available from: https://www.washingtonpost.com/lifestyle/magazine/daniel-amen-is-the-most-popular-psychiatrist-in-america-to-most-researchers-and-scientists-thats-a-very-bad-thing/2012/08/07/467ed52c-c540-11e1-8c16-5080b717c13e_story.html 
12. Cole J, Costafreda SG, McGuffin P, et al. Hippocampal atrophy in first episode depression: a meta-analysis of magnetic resonance imaging studies. Journal of affective disorders. 2011 Nov 1;134(1-3):483-7.
13. Weinberger DR, Torrey EF, Neophytides AN, et al. Lateral cerebral ventricular enlargement in chronic schizophrenia. Archives of General Psychiatry. 1979 Jul 1;36(7):735-9.