1)People who injure themselves have borderline personality disorder (BPD).
This isn't true. There are many people who hurt themselves who are mentally healthy. Lots of the time diagnosing those who self injure as BPD is a cop out for psychiatrists.
2)People hurt themselves for attention.
If this were true, we wouldn't hide our scars or make up stories to explain them. (e.g. my cat did it, I was in a car accident, ect.)
3)Those who hurt themselves are suicidal.
One definition of self harm was stated by Winchel and Stanley (1991)
...the commission of deliberate harm to one's own body. The injury
is done to oneself, without the aid of another person, and the injury
is severe enough for tissue damage (such as scarring) to result. Acts
that are committed with conscious suicidal intent or are associated
with sexual arousal are excluded. By this definition, if you are suicidal, you are not a self injurer.
4)Self injurers grow out of it.
There is not evidence that people who harm themselves simply "grow out of it." It isn't a disorder of their personality.
5)They're all females.
Over the years we have come to realize that the difference between how many females self injure and the number of males are not as different as once thought.
6)It's self inflicted, so it can't be serious.
The degree of the wound cannot measure the emotional pain the person feels.