23rd November 2023

Adversities and Development 

Stress vulnerability model

The stress vulnerability model proposes that individuals with certain genetic or biological vulnerabilities may be more susceptible to the negative effects of stressors, leading to the development of psychiatric disorders.

• Caspi et al. (2003) conducted a longitudinal study of over 1,000 New Zealanders and found that individuals with a genetic polymorphism that reduces the expression of the enzyme monoamine oxidase A (MAOA), which is involved in the regulation of neurotransmitters such as serotonin and dopamine, were more likely to develop depression and antisocial behaviour in response to childhood maltreatment. This study suggests that the interaction between genetic vulnerability and environmental stressors can lead to the development of psychiatric disorders.
• Kendler et al. (1999) conducted a twin study of over 4,000 individuals and found that genetic factors accounted for approximately 50% of the variance in vulnerability to major depression, while environmental factors such as life events accounted for the remaining variance. This study suggests that both genetic and environmental factors contribute to vulnerability to depression.
• Monroe and Simons (1991) conducted a study of individuals with a history of depression and found that those who experienced greater life stressors in the six months prior to a depressive episode had a higher likelihood of relapse than those who experienced fewer stressors. This study suggests that the impact of stressors on depression risk may be particularly strong in individuals with a history of the disorder.

These studies suggest that the stress vulnerability model provides a useful framework for understanding the development of psychiatric disorders and that both genetic and environmental factors contribute to vulnerability to these disorders.

Adverse Childhood Experiences (ACE)

The concept of adverse childhood experiences (ACEs) was developed by Dr. Vincent Felitti and Dr. Robert Anda (1998). They conducted a ground-breaking study that surveyed over 17,000 individuals about their experiences of abuse, neglect, and household dysfunction during childhood, and then correlated those experiences with a range of health outcomes later in life.

ACEs comprise a diverse array of traumatic experiences, including abuse, neglect, household dysfunction, and exposure to community violence. Recent studies have demonstrated that ACEs are alarmingly prevalent, with a staggering two-thirds of participants reporting at least one ACE, and that these experiences exert a profound and long-lasting impact on one’s health and well-being. ACEs have the potential to derail normal developmental processes in childhood, culminating in a host of adverse health outcomes in adulthood, such as chronic physical illnesses, mental health disorders, and addiction.

For example, family instability can affect children to various extents depending on sex (boys affected > girls), age (younger > older) and temperament (hyperactive > placid). This has a demonstrable effect on a child’s cognitive achievements; the most common psychopathology noted is behavioural difficulty. A child who experiences abuse during the sensitive period for attachment (around 6-18 months of age) may struggle to form secure attachments with caregivers, leading to difficulties with emotional regulation and social relationships later in life.

References

• Caspi, A., Sugden, K., Moffitt, T. E., Taylor, A., Craig, I. W., Harrington, H., McClay, J., Mill, J., Martin, J., Braithwaite, A., & Poulton, R. (2003). Influence of life stress on depression: moderation by a polymorphism in the 5-HTT gene. Science (New York, N.Y.), 301(5631), 386–389. https://doi.org/10.1126/science.1083968
• Kendler, K. S., & Baker, J. H. (2007). Genetic influences on measures of the environment: a systematic review. Psychological medicine, 37(5), 615-626.
• Monroe, S. M., & Simons, A. D. (1991). Diathesis-stress theories in the context of life stress research: implications for the depressive disorders. Psychological bulletin, 110(3), 406.
• Felitti, V. J., Anda, R. F., Nordenberg, D., Williamson, D. F., Spitz, A. M., Edwards, V., Koss, M. P., & Marks, J. S. (1998). Relationship of childhood abuse and household dysfunction to many of the leading causes of death in adults. The Adverse Childhood Experiences (ACE) Study. American journal of preventive medicine, 14(4), 245–258. https://doi.org/10.1016/s0749-3797(98)00017-8