Millions of healthy people - including shy or defiant children, grieving relatives and people with fetishes - may be wrongly labeled mentally ill by a new international diagnostic manual, specialists said on Thursday.

In a damning analysis of an upcoming revision of the influential Diagnostic and Statistical Manual of Mental Disorders (DSM), psychologists, psychiatrists and mental health experts said its new categories and "tick-box" diagnosis systems were at best "silly" and at worst "worrying and dangerous."

Some diagnoses - for conditions like "oppositional defiant disorder" and "apathy syndrome" - risk devaluing the seriousness of mental illness and medicalising behaviors most people would consider normal or just mildly eccentric, the experts said.

At the other end of the spectrum, the new DSM, due out next year, could give medical diagnoses for serial rapists and sex abusers - under labels like "paraphilic coercive disorder" - and may allow offenders to escape prison by providing what could be seen as an excuse for their behavior, they added.