Interaction between biological and environmental stresses and their reasons Essay

As research continues, scientists are realizing that the development of several mental disorders are influenced by an interaction between biological and environmental stresses. Major depression and GAD are said to be closely related genetically. They both correlate with the personality traits of neuroticism (N). Kendler et al (2007) performed a study where it was found that the genetic correlation between major depression and generalized anxiety disorder in Swedish twins was estimated at +1.00 in females and +0.74 in males. Participants also shared environmental factors with a correlation of +0.59 in males and +0.36 in females. However, genetic risk factors contributed only around 25% to the genetic correlation between major depression and generalized anxiety disorder. The study showed that the majority of genetic covariance between these disorders results from factors not shared with the personality trait.
The same concept was investigated in another study by Kendler et al (1992), where they used female twins to determine the extent to which two disorders (major depression and generalized anxiety disorder) share common genetic, familial environmental, or individual-specific environmental factors. The results showed that both disorders shared genetic factors completely, suggesting that the liability of major depression and generalized anxiety disorder is influenced by the same genes, and whether a person develops the disease is result of environment.
Reich (1995) replicated these findings on a male population but focused on the participant's family psychiatric histories. He used 119 males and divided them into several groups depending on their clinical diagnosis. Some participants had generalized anxiety disorder (GAD), some had major depressive disorders (MDD), others had both disorders while the rest did not have any clinical diagnosis. The results showed that the GAD and MDD groups had higher levels of family history of depression or anxiety than the other groups. As Kendler, Reich found the similarity of family predisposition of MDD and GAD. However, because the MDD/GAD group had no higher levels of anxiety or depression than the group with no clinical diagnosis, he believes that MDD/GAD could be a separate disorder rather than a combination of MDD and GAD.
Although it is believed that traumatic events trigger PTSD (post traumatic stress disorder), some researchers believe PTSD is heritable. In a study performed by Yehuda et al (2008), the influence of PTSD in mothers and fathers in the presence of PTSD in offspring was examined. Using a psychiatric battery, that identifies and diagnoses traumatic experiences, they evaluated 117 men and 167 women from a community. Of all the participants, 211 were holocaust survivors and 73 were Jewish controls. The participants were divided into groups depending on whether their mother, father or both had been clinically diagnosed with lifetime PTSD. The results showed that maternal PTSD was associated with PTSD and made a greater contribution than paternal PTSD to PTSD risk in adult offspring of Holocaust survivors, although other diagnoses did not show other effects of maternal PTSD. This findings suggests that genes influence the transmission of diseases but there are other factors that might be involved.
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