BRIEF REPORT Brief Report: Plasma Leptin Levels are Elevated in Autism: Association with Early Onset Phenotype? Paul Ashwood Æ Christina Kwong Æ Robin Hansen Æ Irva Hertz-Picciotto Æ Lisa Croen Æ Paula Krakowiak Æ Wynn Walker Æ Isaac N. Pessah Æ Judy Van de Water Published online: 9 March 2007 Ó Springer Science+Business Media, LLC 2007 Abstract There is evidence of both immune dysregu- lation and autoimmune phenomena in children with autism spectrum disorders (ASD). We examined the hormone/cytokine leptin in 70 children diagnosed with autism (including 37 with regression) compared with 99 age-matched controls including 50 typically developing (TD) controls, 26 siblings without autism, and 23 children with developmental disabilities (DD). Chil- dren with autism had significantly higher plasma leptin levels compared with TD controls (p < .006). When further sub-classified into regression or early onset autism, children with early onset autism had signifi- cantly higher plasma leptin levels compared with children with regressive autism (p < .042), TD controls (p < .0015), and DD controls (p < .004). We demon- strated an increase in leptin levels in autism, a finding driven by the early onset group. Keywords Inflammation Á Leptin Á Autism Á Regression Introduction Autism spectrum disorders (ASD) are complex neurodevelopmental disorders distinguished by impaired I. Hertz-Picciotto Á P. Krakowiak Department of Public Health Sciences, Division of Epidemiology, University of California at Davis, Davis, CA, USA L. Croen Department of Research, Kaiser Permanente Northern California, Oakland, CA, USA W. Walker Department of Neurology, University of California at Davis, Davis, CA, USA I. N. Pessah Department of Veterinary Molecular Biosciences, University of California at Davis, Davis, CA, USA Present Address: C. Kwong School of Medicine, Rosalind Franklin University of Medicine and Science, North Chicago, IL, USA P. Ashwood Department of Medical Microbiology and Immunology, University of California at Davis, Davis, CA, USA P. Ashwood Á R. Hansen Á I. Hertz-Picciotto Á P. Krakowiak Á I. N. Pessah Á J. Van de Water The M.I.N.D. Institute, University of California at Davis, Davis, CA, USA P. Ashwood Á R. Hansen Á I. Hertz-Picciotto Á L. Croen Á P. Krakowiak Á I. N. Pessah Á J. Van de Water NIEHS Center for Children’s Environmental Health, University of California at Davis, Davis, CA, USA C. Kwong Á J. Van de Water (&) Division of Rheumatology, Allergy and Clinical Immunology, University of California at Davis, 451 E. Health Sci. Dr., Suite 6510, Davis, CA 95616, USA e-mail: javandewater@ucdavis.edu R. Hansen Department of Pediatrics, University of California at Davis, Davis, CA, USA J Autism Dev Disord (2008) 38:169–175 DOI 10.1007/s10803-006-0353-1 123