IMAGINE waking up every day feeling down, struggling with constant anhedonia (the inability to experience pleasure), facing difficulty in social interactions, and having your memory fail you when you need it the most.
These symptoms are just a glimpse into the reality of depression, making it difficult to thrive in your personal, social and professional life.
According to the World Health Organisation (WHO), major depressive disorder (MDD) is the leading global cause of disease burden, affecting nearly 5% of the world’s population and ranking as one of the top causes of global disability.
The burden of depression is now equally prevalent among adolescents and young adults, indicating an increase in the number of individuals relying on long-term prescribed medication to manage its symptoms.
When discussing mental health disorders, it is crucial to recognise the brain as the organ of
the mind. The challenge lies not in seeking professional help, but in accurately diagnosing the disorder.
Mental health practitioners often utilise thorough assessments and clinical judgements to diagnose mental health disorders. While medical doctors can directly examine the physical organs they treat, they lack the ability to directly assess the organ that controls mental disorders – the brain.
However, with the advancements of technologies, neuroimaging studies are providing us an opportunity to understand depression alongside other severe mental health disorders from multimodal perspectives.
The brain matters
Neuroimaging research has been instrumental in advancing our understanding of depression, offering profound insights into the intricate workings of the brain.
By employing advanced neuroimaging techniques, such as structural and functional magnetic resonance imaging, and electroencephalography, brain scientists have delved deep into neural mechanisms at play.
The technology has allowed us to explore brain pattern activities and structural changes in key regions linked to mood regulations, such as the amygdala and prefrontal cortex.
Let us explore the findings from two non-invasive brain imaging methods: magnetic resonance imaging (MRI), both structural and functional, and electroencephalography (EEG), which can detect brain activity without the need for invasive probes.
The brain’s grey matter, the outermost layer composed of densely packed neurons, serves as the hub for processing and relaying information to other brain regions via interconnected neural pathways.
Structural MRI studies have revealed notable changes in grey matter structure, with reduced thickness observed in individuals with depression compared with their non-depressed counterparts.
Additionally, evidence suggests a correlation between depression and memory impairments, with structural MRI indicating a diminished volume in the hippocampus, a key area responsible for memory storage and retrieval.
Beyond structural differences, functional MRI has shed light on distinct patterns of brain activity in regions such as the anterior cingulate cortex and prefrontal cortex, implicated in functions like planning and decision-making.
Notably, depressed individuals exhibit heightened activity in the amygdala, the brain’s emotions processing centre, when exposed to facial expressions conveying emotions, coupled with decreased activity in the dorsolateral prefrontal cortex, associated with higher-order decision-making processes.
EEG, on the other hand, measures the brain’s electrical activities. These electrical activities are generated at the gaps (synapses) between neurons as a result of the exchange of neurotransmitters and other ions.
Miniscule voltage fluctuations that happen at the neuronal level can then be detected by the electrodes placed on the scalp. EEG distinguishes different frequency bands, each associated with specific brain states.
With regards to depression, high alpha power during sleep is a consistent finding, particularly with those with suicidal ideation.
Additionally, alpha asymmetry, which reflects the difference in alpha band activity between the left and right frontal hemispheres, offers insights into the approach-withdrawal modal – left hemisphere activity is related to approach motivational behaviour while right hemisphere activation suggests withdrawal tendencies.
Although this is an oversimplification of the neurobiological basis of approach motivation behaviours, there are promising findings.
Left alpha activity was found to be prominent among the depressed compared to the non-depressed, suggesting reduced approach motivation, potentially serving as a prognostic indicator for specific symptoms.
Despite the complexity, understanding these neural patterns offers promising avenues for identifying and treating depression.
Promising, but not there yet
So, can neuroimaging reliably detect depression? Yes and No. Why? Because its widespread adoption faces significant barriers.
Firstly, sophisticated neuroimaging tools are rather expensive equipment, which can be costly to purchase and maintain. This means not every hospital and private clinic can afford such equipment.
Furthermore, understanding brain scans and test results is complex and requires specialised trained personnel to make sense of the data. Without proper expertise, there is a risk of misinterpretation, leading to inaccurate diagnoses.
Lastly, there are ethical issues and concerns about privacy, which could lead to potential misuse of sensitive brain data. Compliance with regulations and ethical guidelines adds another layer of complexity, often hindering the widespread use of these methods.
Neuroimaging studies have deepened our understanding of depression. Exploring biomarkers, which are measurable indicators of biological processes, has the potential to transform depression monitoring, diagnosis and treatment.
The future of neuroimaging technology in diagnosing depression holds a remarkable promise. Despite its challenges, the potential benefits cannot be overstated.
I am hopeful that ongoing technological advancements will overcome existing challenges, making these diagnostic tools more widely accessible and affordable to the public, and enabling the development of more tailored and effective treatment strategies.
Academic institutions should prioritise funding and resources for studies that explore the efficacy and applications of neuroimaging tools, and establish strong partnerships with the healthcare sector in the country to facilitate the translation of research findings into clinical practice.
I look forward to a future where neuroimaging technology complements existing diagnostic methods, where we can achieve a more comprehensive understanding of depression.
Dr Hiran Shanake Perera is a
cognitive neuroscientist, and a senior lecturer at the School of Arts and Liberal Sciences,
Faculty of Social Sciences and Leisure Management at Taylor’s University. He is also the deputy director of the Mental Health and Well-being Impact Lab at Taylor’s University.
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