Reading through the books I own on self injury I can see that there are many reasons given as to why we hurt ourselves. One thing that is consistent is that self injury is thoroughly entangled with our emotions. Many self injurers suppress emotion and perhaps come from backgrounds where emotion is not to be expressed, is muted, or downplayed. I know that I do not express emotion very readily, and in fact have now got to the stage where I am uncertain about what emotion I am feeling at any given time. When we suppress our emotions we can get a build-up of those feelings, which can suddenly burst into an uncontrolled mess that we have no idea how to deal with. We can experience suddenly feeling awful and desperate, but with little understanding of why and what has triggered those feelings.
“Self harm is a strategy to cope with, express or reduce intense emotions” 
That is when self injury can come into play, to try to control our emotions, to put them back inside us and stop us facing them. That is one of the reasons people self harm – control. Sometimes the sudden shock of the pain and/or blood can be enough to gain a little control over our lives, even if it is only that part of our lives that we can control.
Various academic studies have shown that self injurers are considerably more likely to have experienced trauma in childhood or as an adult and this can precipitate self injury or induce a relapse. By trauma I mean physical, emotional or sexual abuse, the loss of a parent, family breakup and so on. Quite a number of self injurers have PTSD as a result of the things that have happened to them. However I would like to say that it is dangerous to assume that a adult or child who self injures must have been abused – I, for instance, am thoroughly sick of being asked that by doctors, as I had a perfectly normal childhood.
Self injury is also associated with mental illness (and that does apply to me). Depression and anxiety can both lead a person to self harm. If we are very worried, obsessively thinking and making ourselves more and more anxious then hurting ourselves can break that cycle and give some peace.
Part of the reason why I self injure is that, in that moment, I feel that I deserve punishment, that I am a bad person, that everyone hates me and I should hate myself, too. Sometimes I feel like I am letting the bad stuff in me out when I break the skin. I hate my body, because of how I look and how I would like to look, so I punish my body. People with Body Dysmorphic Disorder are particularly prone to self injury, as you can imagine.
Some people get very angry and frustrated with life, with themselves, and do not know what to do with those emotions, how to deal with them. Many people fear becoming violent, fear being abusive to others and so choose to turn the anger inward, and hurt themselves instead.
For some people, self injury is a form of communication:
“How will you know I am hurting if you cannot see my pain? To wear it on my body tells what words cannot explain.”
That verse is from Corie Blount, and popular with self injurers. Sometimes hurting ourselves gives us permission to say “I am feeling bad”, “I am ill”, “I need help”. It is not, generally, done to bring attention to ourselves, but sometimes it helps me decide that I need to get help, that I really am ill and not just pretending.
Some people have a set routine with their self harm, with specific steps they must go through and meticulous planning. For them, self injury can be quite nurturing. That sounds bizarre, but it is as though they can give themselves permission to look after, to nurse themselves by cleaning wounds and generally comforting themselves, something which they couldn’t do otherwise.
For some, disassociation is the reason they self harm. Disassociation is, as I understand things, an alteration in consciousness, where the person “goes away” and may not remember what they do during that time. Some people find that they have self injured while disassociating, whereas others self harm to get back to reality. Other people, with Disassociative Identity Disorder (DID, once known as multiple personality disorder) may find that different personalities within them may harm them, without their consent. I know very little about DID so I will leave that one there.
In terms of why people continue to self harm, much has been written about the role of endorphins in self injury. Some people say that, because these “feel-good” chemicals are released after injury, and lead to feelings of relaxation, a ‘buzz’ and a lift in mood, that we become addicted to those feelings. Others say that it is more of a psychological addiction, that we become enthralled to the release of pressure we feel, to the ability to help ourselves in this way. I don’t know which is true, or whether both are, but I do feel that self injury can be addictive – I know that I still, when I am anxious or depressed, get the urge to do it again, and it gets harder to resist that urge the worse I feel.
There are many reasons why people self harm, but they are usually to do with emotion, and often to do with self hate. It is not that self injurers are mad or crazy, it is just that we haven’t found a good way of dealing with strong emotion, and we’ve turned to self harm to try to sort it out ourselves. That is why therapy can be very helpful for self injurers, to try to figure out better ways of dealing with our feelings and more positive thoughts. I say this, having not experienced therapy for my self injury!
Self injury comes out of a dark place, and someone who self injures needs help, and compassion. I will talk more in the “recovery” page, but I just want to impress upon anyone who happens to read this that there are real problems which lead to self injury, but that people can and do recover. If something like mental illness is the root of the problem, a damaged view of the self, then it is important to get help for those. As Christians we can and should affirm the worth of the self injurer, that God loves all of us and cares for us very much. We may not be able to love ourselves right now, but God does. Piling on pressure about self injury being a sin would not, I think, be helpful to someone who is already hurting and hating themselves – but talking about how God thinks they are utterly amazing and wonderful, how he bled so they don’t have to, might be.
 Middleton, Kate & Garvie, Sara, “Self Harm: The Path to Recovery” (Oxford: Lion Hudson plc, 2008) p23