The stop thinking about germs, and it

The diathesis-stress model of psychology tries to explain how both nature and nurture affect human behavior. In this lesson, we’ll examine some of the strengths and limitations of the diathesis-stress model.

Diathesis-Stress Model

Olivia has obsessive compulsive disorder, or OCD. She can’t stop thinking about germs, and it makes her really anxious that there are germs everywhere. Sometimes, she even gets panic attacks just thinking about how she’s surrounded by germs.To try to make herself calmer and get rid of her anxiety, Olivia cleans all the time. She scrubs her house from ceiling to floor, trying to eliminate all the germs she can.

Then, she scrubs her own skin raw in order to become clean. But, it’s never enough.What could cause someone like Olivia to develop a mental disorder, like OCD? There isn’t a consensus within the psychological community as to what causes psychological issues. One theory is that problems with a person’s childhood are what cause these types of disorders. For example, one psychologist might say that Olivia’s OCD is a reaction to the stress of having grown up in a messy, chaotic household.Other psychologists, though, believe that disorders like OCD are due to problems with a person’s brain.

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They see Olivia’s problems as being due to differences in her brain.The diathesis-stress model of abnormality says that people are born with a vulnerability to a certain mental illness, and life stressors influence whether they will end up getting that disease or not.For example, perhaps Olivia inherited a gene that makes her more likely to develop OCD than the average person. With just this gene, Olivia might never develop the disorder.

But, if Olivia experiences stress, like having a chaotic childhood, that stress plus her vulnerability could lead to her developing the disorder.Let’s look closer at some of the strengths and limitations of the diathesis-stress model.


For many years, psychologists debated about whether nature or nurture was responsible for mental illness. On one hand, many psychological disorders were linked with anomalies in the brain. But on the other hand, not all disorders have been found to have a biological or genetic basis. And, there are some lifestyle issues, like abuse, bankruptcy, or losing a loved one, that clearly play a part in some psychological issues.

One strength of the diathesis-stress model is that it recognizes the role that both nature and nurture play. Whereas the biological model of abnormality ignores the effect of environment, and the psychodynamic model ignores the effect of biology on psychology, the diathesis-stress model acknowledges that both nature and nurture have an effect on people’s thoughts, feelings, and behaviors.Another strength of the diathesis-stress model is that it explains the results of twin studies in psychology. A twin study is when psychologists look at identical twins, often ones who were raised in separate homes, and compare the instances of mental illness among them.For example, perhaps Olivia was adopted. She has a twin sister who was adopted into a different family.

The girls were adopted as babies and don’t remember each other. But, when they finally meet as adults, they realize that they both have OCD. Clearly, something in their genetics is involved in their psychological disorder.

But wait! Olivia’s friend Sam also has an identical twin. Sam’s twin, Steve, has OCD, but Sam does not. Because identical twins share 100% of the same genes, if OCD was totally genetic, anyone with an identical twin with OCD would also have OCD.But, that’s not the case with mental illness.

Instead, many psychological disorders have a higher incidence between twins, but it’s not 100%. In other words, for many mental disorders, if you have an identical twin with the disorder, you have a higher likelihood of getting it. But, your likelihood is not 100%, even if your twin has it.This suggests that both genetics and environment have an effect on mental illness. The diathesis-stress model offers an explanation for why Sam doesn’t have OCD even though Steve does.

They have the same vulnerability, but Steve has had some type of stress that has combined with that vulnerability to give him OCD.


Despite the strengths, there are a couple of limitations of the diathesis-stress model. For one thing, some people believe that it is too simplistic.

Remember Steve and Sam? They’re twins and share the same genes. Steve has OCD, while Sam does not. The diathesis-stress model says that’s because, even though they share a vulnerability, Steve’s environment leads to more stress, and therefore, he develops the disease.But wait – what if their environment was the same? Steve and Sam, identical twins, could be raised in the same house, go through most of the same life experiences, and still end up very different.In part, this is because people react to events differently.

What Steve finds very stressful may be no big deal to Sam. Because people are complex creatures, the diathesis-stress model might not fully be able to account for why some people develop mental illnesses and others don’t.Another limitation of the model is that no one really knows the exact ways that nature and nurture interact. Some psychologists believe that mental illness develops very soon after a stressor occurs.

A man whose wife leaves him will feel depressed in the days or weeks after she leaves, for example.But, other psychologists point out that sometimes mental illness develops months or even years after stress is experienced. Someone who loses a partner might be okay for a few months, but then begin to develop signs of dementia.

Not knowing exactly how the diathesis-stress model works is a weakness of the model.

Lesson Summary

The diathesis-stress model of abnormality says that people develop psychological disorders as a result of a combination of nature and nurture. There are many strengths of that model, including the fact that it recognizes the role that both biology and environment play in mental health, as well as the fact that it explains the results of twin studies.

But, there are also limitations of the diathesis-stress model, including the fact that it might be too simplistic and that no one really knows the exact ways that nature and nurture interact.

Learning Outcomes

Successfully finishing this video lesson could enable you to:

  • Relate the way in which the diathesis-stress model of abnormality explains the relationship between nature and nurture
  • Assess the strengths and weaknesses of this model

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