Thimerosal and the occurrence of autism: negative ecological evidence from Danish population-based data.

OBJECTIVE It has been suggested that thimerosal, a mercury-containing preservative in vaccines, is a risk factor for the development of autism. We examined whether discontinuing the use of thimerosal-containing vaccines in Denmark led to a decrease in the incidence of autism. DESIGN Analysis of data from the Danish Psychiatric Central Research Register recording all psychiatric admissions since 1971, and all outpatient contacts in psychiatric departments in Denmark since 1995. PATIENTS All children between 2 and 10 years old who were diagnosed with autism during the period from 1971-2000. OUTCOME MEASURES Annual and age-specific incidence for first day of first recorded admission with a diagnosis of autism in children between 2 and 10 years old. RESULTS A total of 956 children with a male-to-female ratio of 3.5:1 had been diagnosed with autism during the period from 1971-2000. There was no trend toward an increase in the incidence of autism during that period when thimerosal was used in Denmark, up through 1990. From 1991 until 2000 the incidence increased and continued to rise after the removal of thimerosal from vaccines, including increases among children born after the discontinuation of thimerosal. CONCLUSIONS The discontinuation of thimerosal-containing vaccines in Denmark in 1992 was followed by an increase in the incidence of autism. Our ecological data do not support a correlation between thimerosal-containing vaccines and the incidence of autism.

[1]  K. Nelson,et al.  Thimerosal and autism? , 2003, Pediatrics.

[2]  J. Lopreiato,et al.  For personal use. Only reproduce with permission from The Lancet Publishing Group. Effect of sunlight and season on serotonin turnover in the brain , 2002 .

[3]  T. Clarkson.  The three modern faces of mercury. , 2002, Environmental health perspectives.

[4]  L. Ball,et al.  An assessment of thimerosal use in childhood vaccines. , 2001, Pediatrics.

[5]  S Bernard,et al.  Autism: a novel form of mercury poisoning. , 2001, Medical hypotheses.

[6]  H Jick,et al.  Mumps, measles, and rubella vaccine and the incidence of autism recorded by general practitioners: a time trend analysis , 2001, BMJ : British Medical Journal.

[7]  J. Powell,et al.  Changes in the incidence of childhood autism and other autistic spectrum disorders in preschool children from two areas of the West Midlands, UK , 2000, Developmental medicine and child neurology.

[8]  P. Mortensen,et al.  The Danish Psychiatric Central Register. , 1997, Danish medical bulletin.

[9]  R. Schoeny,et al.  Mercury study report to Congress. Volume 1. Executive summary. Sab review draft , 1996 .

[10]  T W Clarkson,et al.  Dose-response analysis of infants prenatally exposed to methyl mercury: an application of a single compartment model to single-strand hair analysis. , 1989, Environmental research.

[11]  C. Cox,et al.  Fetal methylmercury poisoning. Relationship between concentration in single strands of maternal hair and child effects. , 1987, Archives of neurology.

[12]  Boardman Reed.  JAMA 100 Years Ago , 1987 .

[13]  M. McCormick,et al.  Immunization Safety Review: Thimerosal-Containing Vaccines and Neurodevelopmental Disorders , 2001 .