Self-injury is defined as any deliberate behavior that causes physical harm but is not done with conscious suicidal intent that a person engages in to manage or decrease emotional distress. Self-injury is something that is often misunderstood, even by helping professionals.
Deb Martinson has created a site, Secret Shame, full of a wealth of information about self-injury. Why do people self-injure?
Self-injury is certainly an issue for many trauma survivors. I understand self-injury as serving a function, as a coping strategy.
People who self-injure may not have developed healthy ways to feel and express emotion or to tolerate distress. Another reason that it is so important that trauma therapy focus on the development of basic skills like identifying and managing emotions. I work with clients in my practice to develop a list of alternatives to self-injury, all the while acknowledging the substitutes may not (especially at first) work as effectively as self-injury did.
If this is an issue for you, please seek help from someone who understands the issue and who can work with you to develop alternatives. It is possible.