To understand how disorders develop we need a conceptual framework to understand the disorder. The Diathesis-stress model is one of the more recent model that give us a way of understanding disorders, the model is also called the Epigenetic model. The Model proposes that people have a genetic tendency for a
behavioral trait inherited from their parents that is activated under certain
environmental conditions. In the textbook Abnormal Psychology: An Integrated Approach written by Barlow and Durand an example is provided of a girl who had “blood-injury-injection phobia”. This girl never
had any episodes of fainting or becoming nauseated at the sight of blood or of
any other injury, until she was unintentionally forced to watch a video of an
animal dissection. This environmental trigger activated the gene expression which altered her behavior. Henceforward, at the mere mention of a cut or blood she would
faint. The Barlow and Durand go on to say that if this girl had never taken a biology
course the gene expression (diathesis) caused by an environmental trigger would have never happened and she would have gone through her
life without knowing of her own tendency for swooning at the sight of blood.
This model allows us to understand how twins possessing identical genetic makeup could in one circumstance develop a disorder and not in the other. Separated at birth, parents divorce, one twin is kidnapped and raised by his captors, there are many possibilities in which twins could be separated and raised in two different environments thus exposing one twin to certain environmental triggers and not to the other. Therefore, one twin experiencing different environment triggers could develop a disorder like clinical depression and the other twin experiencing a different environment could not. According to this model it would all be determined by the environment and the genetic tendencies inherited by that person’s parents.
This model allows us to understand how twins possessing identical genetic makeup could in one circumstance develop a disorder and not in the other. Separated at birth, parents divorce, one twin is kidnapped and raised by his captors, there are many possibilities in which twins could be separated and raised in two different environments thus exposing one twin to certain environmental triggers and not to the other. Therefore, one twin experiencing different environment triggers could develop a disorder like clinical depression and the other twin experiencing a different environment could not. According to this model it would all be determined by the environment and the genetic tendencies inherited by that person’s parents.
Reference
Barlow, David H. & Durand, V. Mark (2008). Abnormal Psychology: An Integrated Approach, CengageNOW™
It's possible, of course, but doesn't the question of the identical twins suggest a more obvious solution? If two people share identical genetics, but different environments, and one develops a "disorder" while the other does not, isn't it most natural to first question the idea that genetics had anything to do with it at all?
ReplyDeleteI'm guessing that in reading this short work, I am entering a larger conversation. Is this hypothesis a concession to an ongoing nature/nurture debate regarding psychological pathology? I assume it was not originally written to stand on its own.
Well, consider the reverse. Researchers have discovered twins separated at birth, living their entire lives apart, reconnected in adulthood who are living virtually identical lives. They look the same, have the same interests and habits, similar family construction, and so on. There are a few recorded cases of this. So, the question is how do we explain this? They had different environments, but similar life outcomes or patterns. Why? The Gene Diathesis-Stress Model has some explanatory power for this set of data, where other models do not. This is a nature and nurture model, not a nature versus nurture model, which is where most are going to in the field of psychological research.
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