Prisoners are particularly vulnerable to developing mental health problems. Histories of abuse, deprivation, homelessness, unemployment and substance misuse are common. Many prisoners have numeracy and literacy problems and a lower than average IQ. In the United Kingdom, more than 70% of the prison population has two or more mental health disorders. A review of 62 prison studies covering more than 23,000 prisoners worldwide found that 3.7 % of all male and 4% of all female prisoners had a psychotic disorder, 10 % of all male and 12% of all female prisoners suffered from major depression, 47 % fulfilled the criteria for an antisocial personality disorder, although there were also high rates of borderline personality disorder. A diagnosis of personality disorder in prisoner populations is strongly associated with substance misuse.