The Mental Health Foundation estimates that nearly half a million people a year across the UK deliberately hurt themselves.
We're not talking DIY accidents, tripping over the furniture or the odd drunken punch at a wall. At its worst, self-inflicted abuse can be as severe as holding a steam iron to the flesh for 90 seconds, gouging out eyes or amputating nipples or fingers.
More commonly, people bite themselves, cut and burn their flesh, pull out their own hair. They often do it regularly, over years and years. Why? As one sufferer put it, it's the only way to stay alive; the "bright red scream" gives relief from intense inner pain.
Marilee Strong's book, the first treatment of this issue for a popular readership, looks at the problem in the United States, where academics estimate that a million people a year are affected, that at least 80 per cent of self-harmers are women, and at least 80 per cent of self-harmers have been abused as children. Practically all also have eating disorders, and a majority have drugs and alcohol abuse problems.
Here, figures are not collected nationally. At a conference of the Association for Professionals in Services to Adolescents last autumn, a consultant psychiatrist estimated the number of young people treated in casualty for deliberate self-inflicted injuries at 20,000 a year. This may reflect only a tenth of the number affected.
Strong illuminates the phenomenon in the US with personal histories. From age four to 12, while Erin's mother lay in a drunken stupor, her grandfather sexually assaulted her with various implements, causing such thick scarring that she can never have children. Growing up with such experiences breeds pain and feelings of powerlessness. Self-mutilation seems the only way to gain control - by getting in first.
Strong interweaves personal stories with crisp precis of theory. Therapeutically, self-mutilation is variously seen as post-traumatic stress, as obsessive-compulsive behaviour, as an aspect of borderline personality disorder or as an addictio. Help can encompass anti-depressant and anti-convulsive medications, one-to-one and group psychotherapy, "tough love" residential care, 12-step "surrender to a higher power" programs like AA and, rarely, self-healing through better relationships.
Some self-harmers find equilibrium, if not relief, in aligning themselves with the "new primitives" body art movement where piercing, branding, scarification and tattooing offer identification with fashion as well as with pain.
Pain is the key. In slashing and burning their own bodies, sufferers seem able to slash and burn a temporary clearing in their psychic briar patch. The body responds to pain with a rush of pleasurable-feeling endorphins: the high blots out inner pain, while the visible blood and scarring placates demonic memories. Because the behaviour is so dramatic, it is hard to give up, yet it is also stigmatising and marginalising. Strong's book ought to leap on to the reading list of anyone involved in pastoral work with adolescents. Those bright red screams want to be heard.
One way of being heard, of getting attention for suffering and bravely surmounting the problems, is to write about it. The other side of American openness to psychic pain is the ease with which princesses of pain jump on the literary bandwagon. One such is Lauren Slater, whose Prozac Diary, published last year, now appears in paperback.
Slater, from a rich and high-achieving but dysfunctional family, has three degrees in psychology as well as several spells in psychiatric hospitals to her credit. Formerly a depressive who slashed her body, starved and binged, had promiscuous, joyless sex and passed her days writing lush prose and counting calories, she is now a productive member of society in a stable relationship, thanks to Prozac. So far, so good.
Sometimes, though, she misses her anguished state and feels less artistically creative with her serotonin take-up sorted out. Tough, eh? However, Slater's writing, much-vaunted for its insights - by herself within Prozac Diary and by others who've read it - is strikingly devoid of that quick empathy which pervades Strong's much more mundane, but much more valuable volume.