Self-injury

Self-injury (SI) or self-harm (SH) occurs when a person hurts their body on purpose. This kind of harm is not suicidal behavior. Many self-harmers hurt themselves because they feel it is the only way to stay alive. However, in some cases the self-harm becomes so bad it can lead to death, and those who self-harm are more likely to commit suicide than those who do not.
There are many different reasons why a person may hurt themselves, though it is often hard to find an exact cause. Sometimes, the self-harm helps relieve unbearable emotions, or feelings of unreality or numbness. Self-harm is often a symptom of other problems. These problems may include physical abuse, sexual abuse, or eating disorders. Self-harm may also stem from mental problems such as low self esteem or perfectionism.
Studying the causes of self-injury can be difficult or inaccurate, because many self-harmers try to hide their injuries.
Types of self-injury.
Self-injury is a general term that includes many different types of deliberate harm to the body. There are many things that can be considered self-harm. If someone works their body too hard, for example, this can be seen as a mild form of self-injury. In other mild cases, a self-harmer may purposely pick off scabs to keep cuts or scratches from healing. Compulsive hair-pulling (trichotillomania) and compulsive skin-picking (dermotillomania) are impulse control disorders which are also mild forms of self-harm. 
In more severe cases, a self-harmer could break or sprain a bone, or lose a dangerous amount of blood. Biting, burning, and cutting are other forms of self-injury. Overdosing on medication is another common type of self-harm.
Self-harm may get worse the longer a person has been doing it. This is because a person's body builds up tolerance to (gets used to) the pain from their injuries. Because of this, they have to hurt themselves more to get the same effect. In some cases, this can lead to fatal or near-fatal injuries.
A person may go through voluntary pain for other reasons that are usually not considered self-injury. A self-inflicted wound is when someone injures themselves to avoid something, not because of psychological problems. Some people give themselves a self-inflicted wound during wartime so that they do not have to serve in the military.
Some people go through pain to change the way they look, such as in ear piercing. This is called body modification. Body modification is not a form of self-injury. 
Scarification is a type of body modification where someone cuts or burns their skin for decoration. This can include branding, which is common in some fraternities. It can also include cutting the skin repeatedly in a pattern or design. This will create very large scars. Some African tribes use scarification as a symbol of beauty and strength.
Self-injury in the population.
Experts estimate that about 1% of the population has self-harmed. While people of all ages and ethnic groups have self-harmed, some groups are more likely to self-harm than others. Age, gender, and race can be factors in the risk of self-injury. Some evidence suggests that self-injury is also more common in people who have a family history of suicide or self-injury.
Age.
In general, more young people are treated for self-injury than any other age group. According to one Australian study 30% of teenagers say they have self-injured. It is more widespread among those with mental illness. One in four (25%) of teenagers with mental illnesses have self-harmed. Self-harm in females is most common between the ages of 15-24. Males are most likely to self-harm through the ages 25-34.
Recent research focusing on young people suggests that 10 percent of 15 to 16 year olds have self-harmed. In this case, the self-harm was usually done by cutting.
Gender.
A study in Oxford in the year 2000 found that approximately 300 per 100,000 (0.3%) of males aged between 15 and 24 years, and 700 per 100,000 (0.7%) of females of the same age, were admitted into a hospital after self-harming. Based on statistics like these, most agree that young white females are most likely to self-injure. Possibly because of this, it is usually believed that women have higher rates of self-harm than men. However, this may not be true because women are more likely to get help for their self-injury. Males may have the same or similar rates of self-injury as women. Some findings have even suggested that in the mid-30s age range, more men are treated for self-harm than women.
Discrimination.
Minority groups who face discrimination are also more likely to self-injure. If someone is bullied because they are different (for example, because of their race, ethnicity or sexual orientation), this can lead to low self-esteem and a feeling of helplessness over emotions. This can lead some people to self-harm.
Personal history.
Studies have show that those who have been abused are more likely to self-injure. Sexual abuse, physical abuse, and emotional abuse can cause low self-esteem, especially in children. It can also cause other emotional problems. Some people may turn to self-harm to relieve these emotions. Low self-esteem in victims of abuse may lead them to believe that the abuse was their fault. They may turn to self-injury because of this.
Unstable living conditions such as unemployment or divorce may also make a person more likely to self-harm.
Prisoners are also more likely to self-harm. This may be because of the ongoing trauma that happens in prisons, including sexual and physical violence and intimidation. In an environment such as prison, where options for inmates are limited, prisoners may turn to self-injury. In England and Wales, a report from The Howard League says that over 22,000 prisoners harmed themselves in 2007.
Those with learning and developmental disabilities such as autism are more likely to self-harm. The cause of this is unclear. Some case studies have shown that it may be a form of self-stimulation. It may be that autistic children who self-harm are trying to express frustration that they cannot explain with words. Autistic children who self-harm may do so by head-banging or biting.
Treatment.
Self-harm is an addictive behaviour. Once someone starts self-injury, it is difficult for them to stop, even if they want to. This makes professional help and treatment an important part of recovery from self-injury.
The type of treatment that is most effective is different from person to person. There are many different types of therapy that have been used to help people that self-harm.
Cognitive-behavioural therapy may help a person understand why they self-harm. Cognitive-behavioural therapy is used to help patients understand the reasons for their problem. This is so that the patient may learn what is causing their self-harm, and learn how to deal with these problems in a way other than self-harm.
Therapies used for post-traumatic stress disorder may also help. This is because many people who self-harm have been victims of abuse. Eye Movement Desensitization and Reprocessing therapy (EMDR) is an example of this.
Drugs may also be used to help treat self-injury. It is thought that self-injury can release chemical endorphins into the brain. Over time, these chemicals can become addictive. There are some drugs that can help with this addiction, but they have not been proven to help people who self-injure. Naltrexone and naloxone are two drugs being researched for this kind of treatment. Research involving endorphins has been mostly done with animals. It is unclear if their brain chemistry changes the outcome of the research.