We read with interest the review article by Fazel & Seewald. ^{Reference Fazel and Seewald1} The authors conclude that severe mental illness is more prevalent in prisoners in low- and middle-income (LAMI) countries than in high-income countries. This may be related to fewer opportunities and services for diverting offenders to health services, a stronger relationship between mental illness and criminality, and different sociocutural factors (e.g. poorer legal representation for the mentally ill in LAMI countries).

We examined in an earlier study the relationship between mental illness and criminality in pre-trial reported Antillean defendants in The Netherlands and The Netherlands Antilles. ^{Reference Vinkers, Heytel, Matroos, Hermans and Hoek2} Defendants who are suspected to have a mental illness are examined pre-trial by a psychiatrist or psychologist both in The Netherlands and The Netherlands Antilles, before diversion to mental health services takes place. We found no significant difference in the prevalence of psychotic disorders among pre-trial reported Antillean suspects in The Netherlands and The Netherlands Antilles (14.4% v. 15.1%) and no significant difference in the prevalence of defendants deemed unaccountable due to a mental disorder (3.9% v. 4.0%). There was, however, a much lower registered crime rate of Antilleans in The Netherlands Antilles than The Netherlands (11 v. 113 offences per year per 1000 persons; P<0.001) and a much higher rate of pre-trial reports in The Netherlands Antilles than The Netherlands (74 v. 8 per 1000 Antillean defendants; P<0.001). Antilleans living in The Netherlands Antilles thus have a low crime rate and a high pre-trial report rate when indicted of a crime compared with Antilleans in The Netherlands, indicating that they are more frequently suspected to have a mental illness.

This finding is in line with the earlier formulated rule of thumb that the frequency of mental illness is higher in countries with low crime rates. ^{Reference Large, Smith, Swinson, Shaw and Nielssen3,Reference Coid4} Indeed, the LAMI countries included in Fazel & Seewald's review have a combined prison population rate of 77 per 100 000, considerably less than the worldwide prison population rate of 145 per 100 000. ^{Reference Walmsley5} The higher prevalence of severe mental illness in prisoners in LAMI countries may be explained by lower rates of crime and imprisonment. If so, the relationship between mental illness and crime is not stronger in LAMI countries, but weaker in high-income countries.