Monday, 28 March 2016

Pop Psychology: Neuroimaging to Diagnose Psychiatric Disorders

One of the biggest misconceptions going around recently within the pop psychology world is the idea that neuroimaging can be used to diagnose a mental health disorder (MHD) such as bipolar or schizophrenia, and whilst research may be interpreted in such a way that may make it seem like that - It is very unlikely to be accurate and reliable.

The thought of something as simple as a brain scan to diagnose something as complex as a MHD is a very, very attractive idea as we always look for palpable evidence in regards to everything - especially health. So there's no doubt that those who don't have the best understanding of how the process works are going to think that this is a sure fire way of getting a diagnosis. It isn't, for several reasons.
1. The brain is so complex we still don't understand how it works.

With our understanding of MHD's ever widening, there are still problems figuring out how they manifest themselves, why they come about and how to treat them. The gaps in our knowledge are vast and have yet to be filled, and although there are studies that show patterns in specific disorders, they cannot be used alone out of the context of the studies they're conducted in. When looking at a study that compares those that suffer from schizophrenia and neurotypical participants, due to the nature of the human brain and natural variations, using the theory outside of an experimental context would be difficult as in the studies there is something to compare against - in real life, we don't have a visual checklist or a specific framework for it.

2. We're still unsure of just how accurate the interpretations of functional imaging are.

The main form of functional imaging is functional magnetic resonance imaging (fMRI) which uses the BOLD (blood oxygenated level dependent) response to measure blood flow to a specific area in the brain - Blood flow to a brain area = activation, so by that logic we assume neural activation which is what we're actually talking about when discussing activity. The problem here is, you can't see the neurons, you can't measure the neurons, we still haven't developed a surefire way to measure the neurons directly, so this method is an indirect measurement of neuronal activity - what this means is: Neurons need blood so wherever there is blood there are neurons, we can't be too sure and we could be completely wrong, but this is all we have at the moment and it's worked for us so far! This is not to say the findings are inaccurate, but a warning/sign to take the results with a pinch of salt as an indirect measurement is not 100%.

3. MHD's like to make friends with other MHD's! Depression, meet anxiety!

A lot of the studies you see will say something along the lines of - "Hey! We found out that those who have depression have smaller amygdalas!" Which would make you think, "Hey, that's cool and easy, now when diagnosing someone with a MHD we just need to look for a smaller amygdala!" - Wrong. The amygdala is involved in a lot of processes, but it's mainly in control of emotions and their regulation - A decrease or increase in amygdala size is bound to cause an effect, and with emotions being implicated in every waking minute of our daily life, then there is no telling what disorder you have just by looking at it, particularly with comorbid disorders. MHD's have a tendency to make friends with other disorders, so more often than not you'll find someone who has depression alongside something else such as OCD, Bipolar, Anxiety etc. In certain disorders such as borderline personality disorder (BPD) the amygdala is also implicated and has also been found to be smaller, so - You go for a brain scan and find that your amygdala is smaller than average - What disorder do you have? Not so easy, right? All of these studies that have been conducted have excluded comorbid disorders or at least controlled them in the results, but in real life that's just not how it works. Comorbidities are very real and very common, making it extremely difficult to diagnose a using neuroimaging unless you are suffering from just ONE disorder - and even then you can't always be too sure. The overlaps between different disorders and brain abnormalities make it almost impossible for doctors to differentiate between which MHD's causing which - Like a crime scene with no witnesses - Without context or understanding you can only assume what's happened using the evidence (brain scans) to piece the story together which of course isn't safe.

4. Drugs, drugs, drugs!

It's no mystery that drugs have a big culture all over the world and despite health and legal implications, it doesn't mean that your flatmate or brother's best friend isn't doing them, selling them or stealing them. It also comes as no surprise that those who suffer from troubles turn to substances (even if it's just alcohol) to disappear from the struggles of life, and in some cases can end up procuring a substance use disorder (SUD). SUD's are extremely common in those suffering from MHD's and in most studies being conducted, those that suffer from them are usually excluded to prevent confounding variables. As illogical as that may seem there is good reason - Substances CAN skew results, and a study looking at brain patterns in schizophrenia or BPD will need to account for any confounds as it can affect the raw results we're looking for, however this poses a problem as realistically many of those suffering from MHD's do abuse drugs and will probably develop a SUD, therefore the results provided can't be applied to real life cases very well. Medications can also have an effect as they are also a drug, and in many cases in studies people are medicated or have been in the past, and it's very difficult to filter for it.

5. Your brain is written in a language that we're still trying to decipher.

The brain is complex, no doubt and scans are only useful for somatic, physically tangible illnesses that can be seen such as brain damage or tumors. You can't "see" depression per say, you can only interpret what's going on with context and hope that you're right. The fact that psychology and MHD's are based on behaviours which are not physically seen on scans make it difficult to use the apparatus to our advantage, which is why the current framework of diagnosing via behavioural assessments is successful and should stay that way. Although they're not perfect as they are subjective, they are based on an objective framework such as the DSM or ICD, and these have been improved over time through trial, error, research and training, so although it's not perfect, it's pretty good considering the gaps in knowledge regarding mental health, and cases of misdiagnosed disorders are usually due to comorbidities or complexities of diagnosing said disorder such as personality disorders, otherwise most people manifest MHD's in a predictable way (ie. Schizophrenia - Hallucinations, disordered thought or Depression - Low mood, insomnia or Anxiety - Palpitations, increased stress etc). 

So, what have we learnt? 

Brain imaging is good for diagnosing somatic and physically tangible illnesses, it is not good for diagnosing psychiatric disorders unless it is being used as an adjunctive tool. 

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