Genetics, Epigenetic Inheritance And Mental Illness

Scientists used biology in response to the 19th century cupola pandemic. Since then, there has been a debate about the extent to which the environment and genetics play a role in psychopathology. In other words, do we get mental disorders because of our genes? Or is it due to our environment? We need to consider both genetics and epigenetic inheritance in order to answer these questions.

It is often suggested that both the environment and genes are responsible for the development of a psychopathological disorder. Is this true? If so, how much weight do they all have? Could certain disturbances be avoided if scientists knew the dominant genes? If a person has one particular gene, do all people who have that same gene develop the same disorder?

In reality, there is usually only one explanation for a particular mental disorder. However, this is a mistake because there are many variables as well as protective and risk factors. For this reason, a one-dimensional perspective is not valid.

In fact, mental disorders are caused by many factors. These are all interconnected. They are biological, psychological and social.  No effect works alone.

The difference between genetics and epigenetic inheritance

We all know how our genes affect behavior. However, we may not know how the environment affects our genes.

Epigenetic inheritance studies the mechanisms that determine whether a gene expresses itself or not. In fact, some people have many genes that they never express, but other people do.

In addition, epigenetic inheritance studies the environment to determine what causes the gene to be expressed. Psychopathology is interested in the relationship between a gene and its environment. This is a phenotype.

Human Genome Project and Schizophrenia

We cannot deny the role of genetics in mental disorders. In fact, genetic factors can explain up to 50 percent of mental disorders.

However, not all people with a similar genetic footprint develop mental disorders. In addition, not all people with a particular mental disorder have the same genetic composition. This is difficult to explain.

Schizophrenia is the mental disorder with the most genetic variance: 50 percent. Other disorders have less genetic variance.

The Human Genome Project found 108 genes associated with schizophrenia. However, none of them were responsive, pathognomonic, or specific. In addition, none had any predictive or diagnostic value. Not only do patients with schizophrenia have these genes, but so do people with bipolar disorder.

At best, only 22 percent of people with schizophrenia had these 108 genes. Other people with schizophrenia did not have them.

Variables that cause gene expression

Epigenetic inheritance does not alter your DNA sequence. However, it varies in the way we express our genes.

Whether or not your genes are expressed depends on certain biochemical conditions. These are affected by your environment. Early experiences can lead to lasting epigenetic memories. In some cases, these pose an increased risk to the development of mental health.

For example, children growing up in orphanages tend to have poorer adjustment and anxiety. They may not suffer from anxiety, but their early experiences have nevertheless increased its risk at some point. We call these epigenetic signs.

Bentall published a study in 2012, after 30 years of work. He found that children who suffer from trauma before the age of 16 are three times more likely to suffer from psychotic experiences.

Trauma appears to produce epigenetic signs that favor the later onset of symptoms. Neglect, abuse, and mistreatment predict mental disorders, especially schizophrenia. This is because they favor the expression of certain genes.

The role of neurotransmitters in mental disorders

Depression is often said to be caused by a chemical imbalance. In addition, when serotonin is released into the bloodstream, depression disappears within a few hours. As in the case of genetic theories, such a hypothesis is far too simple.

People with mental disorders often have too many or too few neurotransmitters. These are usually not the cause of the disease, but a symptom. For example, people with depression have low serotonin levels. Anxious people, on the other hand, have low levels of GABA (gamma-aminobutyric acid) and high levels of noradrenaline and glutamate. Disturbances are not produced by identifiable changes in the specific structures of the brain, nor are they due to an imbalance in these neurotransmitters.

LeDoux and physiological effect on treatments

As mentioned above, mental disorders are caused by a combination of many different factors related to genetics and physiological function. Some researchers have identified specific relevant brain circuits. Their findings contribute greatly to the development of psychopathology.

One example is the American neuroscientist LeDoux. He identified a quick and direct route between the thalamus and the amygdala. This route allows certain emotions to bypass conscious concentration.

New periodic memories are formed between the thalamus and the amygdala. LeDoux identified two sensory pathways between the thalamus and the amygdala for data processing. These two routes are highly adaptive. One is about alarm activity and it deals with threats. The second is slower and handles data that has already been processed well. The amygdala and cortex are asymmetric. Towards the amygdala, the connections are quite weak. However, towards the cortex, the paths are much stronger.

These weak pathways from the cortex to the amygdala mean that therapists do not find cognitive rearrangement particularly useful in the treatment of phobias. For this reason, they believe that systematic exposure or sensitization is more effective. But when the stimulus is social in nature (e.g., aerophobia or public speaking), they find a sensible response more helpful.

This is a clear example of how brain structure affects the development of disorders. Above all, it affects the treatments used. This effect is two-way.

Insel study in primates

Insel conducted a study to determine the effect of the environment on gene expression. He used two groups of monkeys. One group controlled their environmental conditions and the other group did not. Insel gave a benzodiazepine agonist (GABA) to both groups.

Both groups react aggressively, not with fear or anxiety. The control group showed more aggression. These monkeys were all genetically identical. Only their environmental conditions were different. The results suggest that  learning history determines the effect or role of a mediator. In this case, GABA.

Conclusion

Based on the above information, we can conclude the following:

• A genetic predisposition, no matter how dominant it is, never occurs if a person is not exposed to a particular environment.
• Mediators play a role in disorders. However, they do not produce them.
• The effects of learning history are factors in neurobiological relationships that facilitate mental disorders.