Many people around the world suffer from mental disorders. These conditions can impact how a person thinks, feels, and behaves, sometimes altering their perception of reality and making daily life challenging. Mental disorders come in various types, each with distinct characteristics and symptoms.
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How do childhood traumatic events affect mental health in adulthood? A crying girl sitting on the floor
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Diagnosis is carried out by a professional, and treatment options can range from psychological therapy and lifestyle changes to psychiatric medications. While our understanding of these disorders has improved, the underlying causes of their onset remain largely unknown.
Genetics or environment?
The brain is the organ responsible for our thoughts and emotions, and changes in brain function are at the core of mental disorders. But what causes these changes in brain function? Two major factors are genetics and environment. Our DNA—the hereditary material we are born with—affects our predisposition to both physical and mental illnesses.
When a particular illness occurs in several family members, it may be linked to their shared genetic makeup, with a higher risk present from birth. Mental disorders also appear to have a hereditary component: studies of twins have found that if one twin develops a mental disorder, the other twin is more likely to develop it as well, suggesting a genetic influence on the development of these conditions.
While many studies highlight the importance of genetics, there is also substantial evidence that the environment influences the onset of illness. For example, exposure to a hazardous substance can lead to illness, regardless of the DNA inherited from one's parents. In the case of mental disorders, the environment also appears to contribute significantly. Studies indicate that individuals who experienced traumatic events in childhood—such as sexual abuse or growing up in an inadequate environment—are at a higher risk of developing mental disorders later in life.
However, despite the numerous findings suggesting a link between childhood trauma and mental disorders, establishing a clear causal connection is challenging due to the difficulty in separating genetic and environmental influences. Consider, for instance, a family of low socioeconomic status with a high incidence of mental disorders.
Family members may experience increased stress due to financial difficulties, increasing their risk for mental disorders.Yet, because they share a common genetic background that may predispose them to such disorders, it would be hard to distinguish whether the risk is due to genetics, environmental factors, or a combination of both.
Traumatic events can be influenced by both genetics and the environment, and it’s not easy to determine which factor has more impact. A parent with a mental disorder might pass this predisposition to their children through genetics.However, the parent's own mental health challenges could lead to negative behavior, harming the child's living conditions and potentially contributing to the development of a mental disorder in the child by way of abuse or neglect. Inadequate living conditions can also increase the likelihood of experiencing traumatic events.
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Twin studies can help distinguish between the influence of environment and heredity. Pair of identical twin boys
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Cause or effect
The environment in which a child grows up, the traumatic events they experience, and their genetics can all influence the likelihood of developing a mental disorder. When the picture is this complex, it’s difficult to determine how much each traumatic event contributes to this likelihood. However, researchers have a tool that helps them explore this question: long-term tracking of identical twins. Since identical twins develop from the same fertilized egg, they have the same DNA and likely grew up under similar conditions.
Therefore, since both the genetics and the childhood living environment is typically shared among twins, the differences between them are likely due mainly to unique traumatic events that each twin experienced. As a result, if only one twin experiences a traumatic event, researchers can examine how their mental health changes compared to their twin.
Tracking non-identical twins can also provide valuable insights, but since they develop from different fertilized eggs, their genetics are different, and differences between them may also stem from their genetic differences.
Recently, a group of researchers studied identical and non-identical twins to examine whether traumatic events in childhood are linked to a tendency for mental disorders in adulthood. The study included more than 25,000 identical and non-identical (fraternal) twins from Sweden, with an average age of 29.9 years.
The twins answered questionnaires about their childhood experiences, allowing the researchers to determine how many traumatic events each twin had experienced. Medical records were used to identify which twins had been diagnosed with mental disorders, focusing on diagnoses made from the age of 19 to avoid the influence of early-onset disorders on the likelihood of experiencing trauma.
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Identical (monozygotic) twins form from the same fertilized egg and thus have the same DNA, while fraternal (dizygotic) twins do not share the same genetic makeup. Identical and non-identical twins
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Traumatic outcomes
The study revealed a positive correlation between the number of traumatic events experienced during childhood and the likelihood of being diagnosed with mental disorders later in life. The more traumatic events the subjects experienced, the higher their chances of developing a mental disorder.
Specifically, individuals who had not experienced any traumatic events had a 6.4% incidence of mental disorders.In contrast, those who experienced one traumatic event had a 10.2% incidence, those with two traumatic events had a 14.8% incidence, and those with three or more traumatic events had a 24.6% incidence of mental disorders.
Thus, each additional traumatic event increased the likelihood of developing a mental disorder by more than 1.5 times.These results affirm the prevailing understanding and the hypothesis that childhood trauma is linked to the development of mental disorders in adulthood.
The researchers compared twins and examined whether the likelihood of one twin developing a mental disorder increased if they had experienced traumatic events in childhood—and indeed, they found that the likelihood of a twin who experienced a traumatic event developing a mental disorder was 1.2 times higher than that of their sibling, who did not experience such events.
This difference was even greater among non-identical twins, with a 1.72 times higher likelihood. Although statistically significant, the difference was not very large, indicating that shared genetics, living environment, and unique traumatic experiences all influence the likelihood of developing a mental disorder.
The findings of the new study may not be surprising, but the study’s significance lies in its large sample size, which included many pairs of identical and non-identical twins. This allowed for a clearer understanding of how childhood traumatic events influence the likelihood of mental disorders, independent of genetic factors. However, the results suggest that both genetics and childhood living environment affect the likelihood of developing a mental disorder.
Ultimately, it appears that mental health is influenced by a combination of these factors. Since we cannot alter genetics, it is important to ensure that children have a safe and balanced living environment and to protect them as much as possible from traumatic experiences.