The nature versus nurture debate is one of the oldest and most fierce arguments in the field of Psychology. The nature side of the debate argues that behaviour is innate, e.g. inherited via genes, whilst the nurture side suggests that behaviour is learned via experiences and environment. Each side of the argument has their strengths, however they also have significant flaws. As a result, the interactionist approach has been developed to provide a more nuanced explanation of human behaviour. The interactionist approach promotes the idea that the nature and nurture sides of the debate interact together to form behavioural responses. At the heart of the interactionist explanation lies the Diathesis-stress Model. This post will briefly explain how the Diathesis-stress Model works, along with a real-world example to strengthen your understanding of the concept.
What is the Diathesis-stress Model?
The Diathesis-stress Model refers to the idea that behaviour, e.g. psychological disorders, are due to the interaction of an underlying vulnerability and external stressors.
To better understand the Diathesis-stress Model, the term needs to be split into two. Firstly, the term “diathesis” comes from the Greek term for a predisposition. A predisposition results in an increased possibility of a behaviour coming to the surface, e.g. aggression. The main reason for a predisposition is usually related to a genetic variation in one or more genes, which increases susceptibility to behave in a certain way. On the other hand, a predisposition can also be psychological. For example, cognitive distortions and negative thinking patterns.
The term “stress” refers to a life event or series of events that may act as a catalyst for the development of a specific disorder/behaviour, e.g. an abusive childhood. An individual’s diathesis/predisposition interacts with environmental stressors, resulting in behavioural outcomes. It is important to be aware that a diathesis/predisposition may never actually come to light if specific environmental factors are not present. Hence, a diathesis/predisposition does not guarantee specific behaviours within individuals.
The simplest way to understand the Diathesis-stress Model is the popular “Bucket” analogy. The person's diathesis can be compared to a bucket. A person born with a predisposition will have less room in their bucket, subsequently a bucket with a larger amount of space will indicate low vulnerability. Stress can be viewed as water being poured into the bucket. A behaviour such as a mental health issue, occurs when water overflows the rim of the bucket. A person with a diathesis is more likely to run out of bucket space earlier, resulting in a higher chance of developing the behaviour.
Where is the Diathesis-stress Model useful?
The Diathesis-stress Model is highly relevant in the field of psychopathology, which is the scientific study of mental disorders. The Diathesis-stress Model is particularly useful in this field of psychopathology as it allows researchers to observe the interaction between nature (diathesis) and nurture (stress) in terms of developing mental illnesses. The Diathesis-stress Model is highly useful in determining who is likely to develop a disorder and who is not, based on their genetic vulnerabilities and external stressors.
In psychopathology the Diathesis-stress Model is a great way to explain why one individual might have obsessive-compulsive disorder (OCD), whilst the other individual does not, even after being exposed to similar external stressors. A different diathesis/predisposition, e.g. a specific genetic variation, will influence how stress impacts behaviour. In addition, the Diathesis-stress Model is a great way to identify individuals who are at risk of developing mental illnesses. For example, a child from a family with a history of OCD is more likely to be susceptible to the illness.
Example of the Diathesis-stress Model
A great study to show how the Diathesis-stress Model works in the real-world is research by Caspi et al. (2002). Psychologists during this period were already certain that childhood abuse increases the risk of being aggressive/violent in adulthood. However, psychologists could not explain why some children who suffer from poor childhoods do not go on to display antisocial behaviour into adulthood. Caspi wanted to know if genetics play a key role in resilience to abusive treatment?
Caspi’s study used a large sample of male children who were followed longitudinally from birth to adulthood. Each child was examined in terms of experiencing abuse/neglect during childhood. In addition, Caspi looked at the MAOA gene. A dysfunctional MAOA gene has been linked to impulse control, hence people with this gene variation are more likely to be aggressive/violent (diathesis). Caspi found that genes alone did not result in antisocial behaviour in adulthood, and childhood abuse alone was not enough to guarantee aggression/violence. On the other hand, children who experienced both a dysfunctional MAOA gene and childhood abuse were the ones who went on to suffer.
Research by Caspi is one of the most famous studies in relation to the Diathesis-stress Model as it provided one of the empirical pieces of evidence of the gene and environment interaction. The research clearly displayed how a genetic vulnerability (dysfunctional MAOA) and an external stressor (abuse) combine to increase susceptibility to aggressive/violent behaviour in adulthood.
Conclusion of the Diathesis-stress Model
The Diathesis-stress Model is a fascinating concept, which provides a strong framework for how specific behaviours are formed. For decades psychologists have tried to explain human behaviour using a nature or nurture cause alone. This is an overly simplistic approach and humans are complex beings, consequently the Diathesis-stress Model is a far more reflective approach to explaining behaviour. Arguing that behaviour is due to genetics or environment alone is in the past, modern explanations that acknowledge these two factors in conjunction are far more powerful and provide a more complete picture of human behaviour.
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