The exact bounds of self-harm are imprecise, but generally exclude tissue damage that occurs as an unintended side-effect of eating disorders or substance abuse, as well as more societally acceptable body modification such as tattoos and piercings.

The motivations for self-harm vary; some use it as a coping mechanism to provide temporary relief of intense feelings such as anxiety, depression, stress, emotional numbness, or a sense of failure.

Other approaches involve avoidance techniques, which focus on keeping the individual occupied with other activities, or replacing the act of self-harm with safer methods that do not lead to permanent damage.

[19] This differentiation may have been important to both safeguard the reputations of asylums against accusations of medical neglect and to protect patients and their families from the legal or religious consequences of a suicide attempt.

[19] In 1896, the American ophthalmologists George Gould and Walter Pyle categorized self-mutilation cases into three groups: those resulting from "temporary insanity from hallucinations or melancholia; with suicidal intent; and in a religious frenzy or emotion".

Some branches of Islam mark the Day of Ashura, the commemoration of the martyrdom of Imam Hussein, with a ritual of self-flagellation, using chains and swords.

Kikuyu girls cut each other's vulvas in the 1950s as a symbol of defiance, in the context of the campaign against female genital mutilation in colonial Kenya.

[30] Ross and McKay (1979) categorized self-mutilators into nine groups: cutting, biting, abrading, severing, inserting, burning, ingesting or inhaling, hitting, and constricting.

[32] Walsh and Rosen (1988) created four categories numbered by Roman numerals I–IV, defining Self-mutilation as rows II, III and IV.

Practices are historically transient and cosmetic such as piercing of earlobes, nose, eyebrows as well as male circumcision while deviant self-mutilation is equivalent to self-harm.

Some sources define self-harm more broadly than self-injury, such as to include drug overdose, eating disorders, and other acts that do not directly lead to visible injuries.

[53] Other self-harm methods include burning, head-banging, biting, scratching, hitting, preventing wounds from healing, self-embedding of objects, and hair-pulling.

[63] An estimated 30% of individuals with autism spectrum disorders engage in self-harm at some point, including eye-poking, skin-picking, hand-biting, and head-banging.

[66] Abuse during childhood is accepted as a primary social factor increasing the incidence of self-harm,[67] as is bereavement,[68] and troubled parental or partner relationships.

[9][11][69][70] Other predictors of self-harm and suicidal behavior include feelings of entrapment, defeat, lack of belonging, and perceiving oneself as a burden along with having an impulsive personality and/or less effective social problem-solving skills.

[9][71][page needed] Two studies have indicated that self-harm correlates more with pubertal phase, particularly the end of puberty (peaking around 15 for girls), rather than with age.

[74][75] The most distinctive characteristic of the rare genetic condition Lesch–Nyhan syndrome is uncontrollable self-harm and self-mutilation, and may include biting (particularly of the skin, nails, and lips)[76] and head-banging.

[82] A 2021 meta-analysis on literature concerning the association between cannabis use and self-injurious behaviors has defined the extent of this association, which is significant both at the cross-sectional (odds ratio = 1.569, 95% confidence interval [1.167-2.108]) and longitudinal (odds ratio = 2.569, 95% confidence interval [2.207-3.256]) levels, and highlighting the role of the chronic use of the substance, and the presence of depressive symptoms or of mental disorders as factors that might increase the risk of self-injury among cannabis users.

[89] In older adults, influenced by a combination of interconnected individual, societal, and healthcare factors, including financial and interpersonal problems and comorbid physical conditions and pain, with increased loneliness, perceived burdensomeness of ageing, and loss of control reported as particular motivations.

[94][medical citation needed] Those who engage in self-harm face the contradictory reality of harming themselves while at the same time obtaining relief from this act.

[95] Studies of clinical and non-clinical populations suggest that people who engage in self-harm have higher pain thresholds and tolerance in general, although a 2016 review characterized the evidence base as "greatly limited".

[115] In individuals with developmental disabilities, occurrence of self-harm is often demonstrated to be related to its effects on the environment, such as obtaining attention or desired materials or escaping demands.

[119] Techniques, aimed at keeping busy, may include journaling, taking a walk, participating in sports or exercise or being around friends when the person has the urge to harm themselves.

[129] This contrasts with previous studies, which suggested that up to four times as many females as males have direct experience of self-harm,[9] which many had argued was rather the result of data collection biases.

However, this discrepancy has been known to vary significantly depending upon population and methodological criteria, consistent with wide-ranging uncertainties in gathering and interpreting data regarding rates of self-harm in general.

For example, feminist author Barbara Brickman has speculated that reported gender differences in rates of self-harm are due to deliberate socially biased methodological and sampling errors, directly blaming medical discourse for pathologising the female.

Though an important case study is that of Sri Lanka, which is a country exhibiting a high incidence of suicide[142] and self-poisoning with agricultural pesticides or natural poisons.

Great potential for the reduction of self-harm lies in education and prevention, but limited resources in the developing world ultimately make these methods challenging.

[17] Zoo or laboratory rearing and isolation are important factors leading to increased susceptibility to self-harm in higher mammals, e.g., macaque monkeys.

[17] For example, pemoline, clonidine, amphetamine, and very high (toxic) doses of caffeine or theophylline are known to precipitate self-harm in lab animals.