because accurate reporting is seen as stigma tizing, or because the behaviors are experi-
enced positively by the individual who engages in them, who is unmotivated to receive
treatment. Young children might experiment wi th these behaviors but not experience re-
lief. In such cases, youths often report that  the procedure is painful or distressing and
might then discontinue the practice.
Development and Course
Nonsuicidal self-injury most often starts in the early teen years and can continue for many
years. Admission to hospital for nonsuicida l self-injury reaches a peak at 20–29 years of
age and then declines. However, research that  has examined age at hospitalization did not
provide information on age at onset of the behavior, and prospective research is needed to
outline the natural history of nonsuicidal self-injury and the factors that promote or in-
hibit its course. Individuals often learn of th e behavior on the recommendation or observa-
tion of another. Research has shown that wh en an individual who engages in nonsuicidal
self-injury is admitted to an inpatient unit, other individuals may begin to engage in the
behavior.
Risk and Prognostic Factors
Male and female prevalence rates of nonsuicida l self-injury are closer to each other than in
suicidal behavior disorder, in which the female-to-male ratio is about 3:1 or 4:1.
Two theories of psychopathology—based on functional behavioral analyses—have been
proposed: In the first, based on learning theo ry, either positive or negative reinforcement
sustains the behavior. Positive reinforcement might result fr om punishing oneself in a way
that the individual feels is de served, with the behavior induci ng a pleasant and relaxed state