Intergenerational Trauma

Intergenerational trauma (IT) refers to effects of trauma that are passed down from a trauma survivor to their descendants. IT can be the result of repeat behaviors, such as parenting styles, family environments, and even cycles of abuse. In this way, social learning theory (the idea that behaviors can be developed by observing and imitating others) can be applied to partially explain some IT. For example, having post-traumatic stress disorder (PTSD), anxiety, or depression from a traumatic event may affect one's parenting behaviors. Children parented in this environment are shaped by these parenting behaviors and may mimic these behaviors in adulthood. Another example is the trauma passed through cycles of abuse. For example, when a victim of child abuse becomes a parent they may mimic the same parenting techniques and patterns of abuse to their offspring. In this way, trauma perpetuates through generations by way of repeat behaviors, social interactions, and family environments. 

However, IT can also be passed on through epigenetic changes. Epigenetic changes are changes to gene expression through DNA methylation and histone modifications without changes to the underlying DNA sequence. Gene expression describes which genes are expressed (or "turned on") and which genes are not expressed (or "turned off"). Gene expression impacts the production of proteins and other cellular functions. Traumatic experiences can alter gene expression related to the stress response system, emotional regulation, and other cognitive processes that may ultimately contribute to mental, emotional, and even physical health. These epigenetic changes can be hereditary, meaning that they can be passed from one generation to the next. In this way, the effects of traumatic experiences can be passed from parent to child, grandchild, and so forth. 

The most studied example of IT is in the descendants of Holocaust survivors. Studies have shown that children and grandchildren of Holocaust survivors have altered stress hormones, and a higher prevalence of depression, PTSD, anxiety disorders.