<P> A 2005 review of prior surveys in 46 countries on the prevalence of schizophrenic disorders, including a prior 10 - country WHO survey, found an average (median) figure of 0.4% for lifetime prevalence up to the point of assessment and 0.3% in the 12 - month period prior to assessment . A related figure not given in other studies (known as lifetime morbid risk), reported to be an accurate statement of how many people would theoretically develop schizophrenia at any point in life regardless of time of assessment, was found to be "about seven to eight individuals per 1,000" (0.7 / 0.8%). The prevalence of schizophrenia was consistently lower in poorer countries than in richer countries (though not the incidence), but the prevalence did not differ between urban / rural areas or men / women (although incidence did). </P> <P> Studies of the prevalence of personality disorders (PDs) have been fewer and smaller - scale, but a broader Norwegian survey found a similar overall prevalence of almost 1 in 7 (13.4%), based on meeting personality criteria over the prior five - year period . Rates for specific disorders ranged from 0.8% to 2.8%, with rates differing across countries, and by gender, educational level and other factors . A US survey that incidentally screened for personality disorder found an overall rate of 14.79% . </P> <P> Approximately 7% of a preschool pediatric sample were given a psychiatric diagnosis in one clinical study, and approximately 10% of 1 - and 2 - year - olds receiving developmental screening have been assessed as having significant emotional / behavioral problems based on parent and pediatrician reports . </P>

The most common mental disorder in childhood is ____