Biological Sciences

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Evidence for genetic basis of schizophrenia

-Kingson Wilson

The Biochemical Basis of Schizophrenia

Schizophrenia is a chronic mental disorder we often hear about, and while many of its associated symptoms such as hallucinations and paranoia are well-known, few of us have given much thought to what causes the disorder. Over 50 million people worldwide live with schizophrenia, with chances of developing the disorder being highest in the early or mid-20s for men, and in the late 20s for women. Understanding this disorder (and mental health issues in general) is the first step toward being more sensitive toward affected individuals around us. The symptoms of schizophrenia vary in wide range, and commonly include:

  • • Disoriented thinking, emotions and behavior, resulting in mood swings, detachment etc.
  • • Loss of contact with reality
  • • Hallucinations, most commonly auditory hallucinations
  • • Difficulties in communication
  • • Paranoia

What do scientists know so far about the biochemical basis of the disease? There is evidence to suggest that schizophrenia is linked to changes in the activity of chemicals in the brain called neurotransmitters. Scientists think overly responsive dopamine systems may affect the brain in such a way that causes hallucinations and other symptoms. Dopamine is a neurotransmitter that influences movement, learning, attention and emotions. Patients with schizophrenia are often diagnosed with extra receptors for dopamine in their nervous systems. Neurotransmitters work by binding to receptors on specific cells, and an increase in the number of receptors makes the cells more sensitive to the effects of the neurotransmitter. For example, the buzz you get after beating your friend on FIFA 16 is actually dopamine in your nervous system that rushes inside you and makes you feel happy. Due to these associations, dopamine blocking drugs are used as anti-psychotic medications in treatment. Alongside dopamine, the activity of other neurotransmitters such as serotonin, Gamma-aminobutyric acid (GABA), glutamate/N-methyl-D-aspartate (NMDA), acetylcholine, and norepinephrine have also been implicated in various studies.

What, then, are the physiological manifestations of the biochemical imbalance? Research shows that schizophrenics are often diagnosed with high activity in the thalamus of the brain, which alters sensory signals and could cause hallucinations. The thalamus is located between the cerebral cortex and the midbrain. It regulates voluntary motions, like consciousness and the sleep/wake cycle. It is also responsible for other senses like sound, taste, touch and the sense of a person sitting beside you. Most of the signals from the thalamus go to the eyes, ears, mouth and skin.

Another region of the brain that is thought to be involved is the amygdala. There are two amygdalae in brain. The amygdalae are on opposite sides of the brain’s medial temporal lobe. They are associated with emotions, fight-or-flight instincts, and pleasure. Aberrant activity results in unbalanced production of neurotransmitters. Patients with schizophrenia have abnormally high levels of activity in the amygdala, which is strongly associated with paranoia.

Schizophrenia is a disorder which is influenced by genetics. The probability of developing the disorder are one in a hundred, but if a sibling or a parent has it, the odds jump to one in ten. However, schizophrenia can occur regardless of family history. Here, other factors come into account. It can be the environment of the patient, for example, stress or trauma. Current evidence suggests that a combination of genetic makeup and environmental stress contribute to the onset of schizophrenia. This means that people with genetic vulnerability will not necessarily develop schizophrenia but people without known family history could still develop the disorder due to environmental factors, such as poverty.

Several studies have tried to identify the genes that increase predisposition to schizophrenia. A recent study published in Nature by the Schizophrenia Working Group of the Psychiatrics Genomics Consortium compared more than 35,000 people living with schizophrenia with more than 110,000 people without the disorder from 35 different countries, and discovered more than 100 genes that are associated with, and potentially responsible for, the development of the disorder. Though most of these genes code for dopamine regulation, others code for immune system functioning. Scientists are still working on how the genes coding for immune system can be responsible for schizophrenia.

Today, people suffering from schizophrenia can achieve proper care and live with the disorder to lead almost a normal life. They are supported by professionals that help them cope with the condition. Understanding the disease is a work in progress and new hypotheses are being proposed more frequently, which will hopefully lead us to positive outcomes regarding this disorder. According to WHO, one out of two people suffering from schizophrenia do not receive proper treatment. Getting rid of the stigma associated with schizophrenia and mental health disease in general would promote better delivery of care to affected individuals.

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