Illnesses Associated with SI
Self-Injury has been linked to a variety of mental illnesses, being a method of coping with each. These include:
Multiple Personality Disorder (aka Disassociative Identity Disorder)
Borderline Personality Disorder
Bipolar Disorder (aka Manic Depression)
Eating Disorders (anorexia, bulimia, overeating etc)
Post-Traumatic Stress Disorder (PTSD)
Autism (also Asperger's Syndrome)
Not all self-injurers have a mental health problem, any mental health problem. However, it seems that the majority have had at least a brush with mental illness - most commonly Borderline Personality Disorder and depression. SI is actually one of the "symptoms" of BPD.
It seems as though SI is used as a maladaptive coping mechanism for these various illnesses - for example the feelings of worthlessness common in depression may be taken out on the skin in SI, disassociation is a common feature of SI, where the sufferer becomes unaware of his/her actions, feeling as though they were watching from far off, or not even remembering their SI.
Treatment of SI often involves treating the underlying disorder in the belief that once that trigger is gone, the sufferer will no longer feel any need to SI.
In addition SI has been strongly linked to childhood sexual, physical or emotional abuse, or neglect, with around 60% of sufferers having experienced this. Emotional repression has also been linked to it, if you cannot tell others of your problems, cutting your skin becomes a possible outlet of feelings.