Scientific studies have shown that genetics play an important role in susceptibility to developing schizophrenia. People with a first-degree relative (parent, sibling) with schizophrenia have a significantly higher risk of developing the disease compared to the general population. This risk increases even more if there are multiple affected relatives and if we stimulate our environment with risk factors such as drug consumption.
What is schizophrenia and what are its symptoms?
Schizophrenia is a chronic and severe mental disorder that affects 1% of the population, altering the way a person thinks, feels, and behaves. It is characterized by a combination of hallucinations, delusions, and thought and behavior disorders that impair a person's ability to function effectively. Sometimes, patients exhibit a lack of motivation, reduced emotional expression, social withdrawal, and difficulty experiencing pleasure.
How hereditary is schizophrenia?
The exact cause of schizophrenia is unknown, but it is believed to result from a combination of genetic factors (its heritability is around 70%), biological and environmental factors.
There are various genetic variants that modulate the risk of developing schizophrenia, providing greater or lesser genetic predisposition to the development of the disease. Among these variants, we find variants located in genes such as:
- CACNA1C and CACNB2: These genes provide instructions for making calcium channels. Calcium ions are important for many cellular functions, such as cell communication, muscle contraction, and the regulation of certain genes, particularly those involved in brain development.
- GRIA1: expresses glutamate receptors. Glutamate is the most common excitatory neurotransmitter and is involved in a wide variety of brain functions such as memory, learning, and brain plasticity in the cerebral cortex. Variants in the GRIA1 gene may predispose to alterations in glutamatergic signaling, which regulates neurological excitation in the human nervous system.
- TCF4: This gene is widely expressed and plays an important role in the development of the nervous system. Variants in the TCF4 gene have been associated with an increased risk of schizophrenia.
These variants can be analyzed through genetic tests such as those from ADNTRO, which allows you to know your genetic predisposition to developing schizophrenia.
How do drugs affect the development of schizophrenia?
The use of certain drugs (environmental factors) can increase the risk of developing schizophrenia or trigger psychotic episodes in genetically predisposed individuals. The most common drugs are:
- Cannabis: Cannabis use, especially during adolescence (a critical period of brain development), has been associated with an increased risk of developing schizophrenia. THC, the main psychoactive component of cannabis, can alter brain function and trigger psychotic symptoms in genetically predisposed individuals. This drug affects the glutamatergic system among others, potentially increasing the risk of psychosis in individuals with variants in the GRIA1 gene among other genes.
- Amphetamines: These substances can induce psychotic symptoms similar to those of schizophrenia, such as hallucinations and delusions. Prolonged and abusive use can cause lasting changes in brain chemistry and increase the risk of psychosis.
- Cocaine: Cocaine can cause psychosis and symptoms similar to those of schizophrenia, especially in high doses or with chronic use. It affects dopamine, a neurotransmitter that, according to the dopaminergic hypothesis, is implicated in schizophrenia. The dopaminergic system can become hyperactive, which is associated with positive symptoms of schizophrenia, such as hallucinations and delusions. In vitro studies have observed a lower amount of CACNA1C protein after cocaine exposure, reducing calcium channels that are crucial for neurons.
The aforementioned drugs can cause neuroinflammation by activating microglia. Microglia are neuronal support cells that act as part of the brain's immune system. Neuroinflammation, an inflammatory response in the brain, is linked to various neuropsychiatric disorders, including schizophrenia.
