Central nervous system (CNS) prophylaxis involving cranial irradiation has frequently been found to result in cognitive deficits in survivors of childhood acute lymphoblastic leukaemia. The existence of this effect is still controversial, however, as is the question of factors that might affect its severity. The literature is surveyed and a meta-analysis undertaken on 30 IQ comparisons, which shows a substantial average decrement in irradiated subjects. The effect is larger when radiation is administered at a younger age and appears to be progressive. The effect may comprise two elements, one common to young cancer patients and one specific to CNS prophylaxis.
The study tested hypotheses that from 1964 to 1993: (1) suicide rates among Australian 15- to 24-year-old males rose more sharply in rural than metropolitan areas; (2) firearm suicide rates among 15- to 24-year-old males, declining throughout Australia recently, rose continuously in rural areas; (3) suicide rates among 15- to 24-year-old females did not change significantly in either metropolitan or rural areas. Suicides of those aged 10-24 years recorded by the Australian Bureau of Statistics (ABS) were classified according to the subject's residential grouping. Rates were calculated using ABS population data corresponding to these groupings. Results were analysed using log-linear analysis and chi-square statistics. The results supported the first two hypotheses, but not the third. Suicide rates for 15- to 24-year-old males rose by a factor of 2.2 in metropolitan areas, by 4-fold in towns with populations between 4,000 and 25,000, and by 12-fold in towns with populations less than 4,000. Male firearm suicide rates continued to rise in rural areas, and the greatest proportion of deaths in those locations were by firearms, though male hanging rates increased most in recent years in all locations. Female youth suicide rates did not change overall, but in towns with populations less than 4,000, they increased 4.5-fold. Possible explanations for this epidemic, which are mostly speculative and require confirmation, are discussed.
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