Neuroscience: Why we cannot explain psychopathology based only on genes

This is a simple article to explain highly complex subjects: neuroscience, psychopathology and genetics. The question is, why, despite decades of progressive molecular biological research, we cannot exclusively answer psychopathology / mental disorders not caused entirely by organic conditions, by looking at genes alone. Although there are numerous twin studies for mental disorder, the results are inconclusive.

The diagram below describes the simplistic idea to a comprehensive concept of genetics linking to mental disorder (psychopathology).

It would have been easy if we could identify a gene for each disorder, as in (a). With issues of the psyche, it is much more complex. The nature of genes is that genes switch on and off, and what gets transcribed from genes into proteins are very dependent on the environment in which the individual lives in and the experiences (consequence of time / relationships / fate).

The image below describes how the environment / perceptions and social interactions affect gene expression and the condition of the neurocircuits in the brain.

The graphic below explains how multiple experiences and the type of life experiences affect gene expression and hence the severity of a psychological symptom.

The diagram below further illustrates the effects of stress on gene expression leading to neurological consequences that lead to setting up of psychiatric disorders.

The image below shows that the genotype (and hence the quality of certain essential proteins) plays a role in susceptibility to disorder.  No man is created equal, in other words.

Which genes are responsible for what disorder? The diagram below is an illustration that disorders are complex and involve the expression of different genes.  These genes affect different biochemical pathways. In order to put a finger on which pathway leads to what consequence is complex and may not hold true for all persons suffering the same symptoms.

That said, the type of genetic make-up leads to susceptibility to a disorder. This is because the proteins that are involved in neuro circuitry, may differ in structure in different individuals (are polymorphic) even if these have the same function. The polymorphism explains why some people are more likely to get the disorder. The graphic below also explains to us that environmental factors play important role.

The diagram below repeats the same message as the previous diagram.

In conclusion, genes are simply there to be coded. The coding, however does not tell us a whole lot about the individual because the expression of the genes are regulated. Not all genes are expressed at all times, and how they are regulated is dependent on the experience of the individual’s environment / social situation and structure / family history, health, etc. Furthermore psychopathology is very complex, and in the molecular sense involves complicated biochemical pathways which are constantly being regulated. It is however true that some people are predisposed to certain conditions, however the severity of the symptoms (or if there are symptoms at all) is dependent on the environment.

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