Family History & Your Genetics
Because many mental illnesses tend to run in families, researchers have been searching for specific genes, passed down through generations (heredity) that may increase a person's chance of developing the illness.
The evidence that heredity plays a role in the development of some forms of mental illness has been discovered by studying identical twins who were raised separately, identical twins are genetically identical but have had different nurturing environments and non-identical twin children (related but genetically different) of mothers with different forms of severe mental illness. These different types of twins are then compared in their risk for developing a severe mental illness against the general public who do not have a mental illness.
Evidence from twin studies
If an identical twin that is raised separately from its other twin develops schizophrenia, the chance that the second twin will also develop the condition is 50%, or 1 chance in 2. In non-identical twins however, (who would share on average only half of their genetic makeup) when one twin develops schizophrenia, there is only a 15% chance that the other twin will also develop the disorder.
While this risk is higher than for the general population (who have about 1 chance in 100 or 1%) of developing the condition, it suggests that heredity is not the only factor influencing the development of schizophrenia in these families otherwise twin study results would show a 100% risk between identical twins (you may hear this referred to as concordance)
What exactly is inherited?
The neurotransmitter system
The chemical messenger system of the body, has received a great deal of attention as a possible cause of schizophrenia. Researchers have known for decades that there is a link between neurotransmitters and schizophrenia, because drugs which alter these transmitters also relieve symptoms of schizophrenia. Some studies hypothesize that a low or high level of a specific neurotransmitter such as dopamine and serotonin is the cause. Others indicate that an imbalance of these substances is the problem. Other studies have found that a change in the sensitivity of the receptors on nerve cells that receive the neurotransmitter messages is at least part of the cause of schizophrenia.
Metabolism
There is also some evidence that genetic factors may influence the membrane structures and metabolism of nerve cells within the body. The structure of the membranes around neurones is dependent upon levels of certain essential fatty acids in the blood. People with schizophrenia have been found to have lower levels of these fatty acids.
Genetic changes & deletions
There is also some genetic evidence pointing towards ‘deletions’ (parts missing) of different chromosomes in an individual's DNA. One study publicised about this genetic factor claimed that part of the chromosome that was responsible for creating the protein used to breakdown one neurotransmitter in the brain was missing in the people within the study that later developed schizophrenia.
The evidence that heredity plays a role in the development of some forms of mental illness has been discovered by studying identical twins who were raised separately, identical twins are genetically identical but have had different nurturing environments and non-identical twin children (related but genetically different) of mothers with different forms of severe mental illness. These different types of twins are then compared in their risk for developing a severe mental illness against the general public who do not have a mental illness.
Evidence from twin studies
If an identical twin that is raised separately from its other twin develops schizophrenia, the chance that the second twin will also develop the condition is 50%, or 1 chance in 2. In non-identical twins however, (who would share on average only half of their genetic makeup) when one twin develops schizophrenia, there is only a 15% chance that the other twin will also develop the disorder.
While this risk is higher than for the general population (who have about 1 chance in 100 or 1%) of developing the condition, it suggests that heredity is not the only factor influencing the development of schizophrenia in these families otherwise twin study results would show a 100% risk between identical twins (you may hear this referred to as concordance)
What exactly is inherited?
The neurotransmitter system
The chemical messenger system of the body, has received a great deal of attention as a possible cause of schizophrenia. Researchers have known for decades that there is a link between neurotransmitters and schizophrenia, because drugs which alter these transmitters also relieve symptoms of schizophrenia. Some studies hypothesize that a low or high level of a specific neurotransmitter such as dopamine and serotonin is the cause. Others indicate that an imbalance of these substances is the problem. Other studies have found that a change in the sensitivity of the receptors on nerve cells that receive the neurotransmitter messages is at least part of the cause of schizophrenia.
Metabolism
There is also some evidence that genetic factors may influence the membrane structures and metabolism of nerve cells within the body. The structure of the membranes around neurones is dependent upon levels of certain essential fatty acids in the blood. People with schizophrenia have been found to have lower levels of these fatty acids.
Genetic changes & deletions
There is also some genetic evidence pointing towards ‘deletions’ (parts missing) of different chromosomes in an individual's DNA. One study publicised about this genetic factor claimed that part of the chromosome that was responsible for creating the protein used to breakdown one neurotransmitter in the brain was missing in the people within the study that later developed schizophrenia.
