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Secular changes in the symptom level of clinically diagnosed autism
Author(s) -
Arvidsson Olof,
Gillberg Christopher,
Lichtenstein Paul,
Lundström Sebastian
Publication year - 2018
Publication title -
journal of child psychology and psychiatry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.652
H-Index - 211
eISSN - 1469-7610
pISSN - 0021-9630
DOI - 10.1111/jcpp.12864
Subject(s) - autism , psychology , psychiatry , developmental disorder , neurodevelopmental disorder , pediatrics , medical diagnosis , clinical psychology , medicine , pathology
Background The prevalence of autism has been reported to have increased worldwide. A decrease over time in the number of autism symptoms required for a clinical autism diagnosis would partly help explain this increase. This study aimed to determine whether the symptom level of clinically diagnosed autism cases below age 13 had changed over time. Methods Parents of Swedish 9‐year old twins ( n = 28,118) participated in a telephone survey, in which symptoms and dysfunction/suffering related to neurodevelopmental disorders [including autism, but also attention‐deficit/hyperactivity disorder ( ADHD ), Developmental Coordination Disorder ( DCD ), and Learning Disabilities ( LD )] in their children were assessed over a 10‐year period. Survey data was merged with the National Patient Register containing clinically registered autism diagnoses ( n = 271). Results In individuals who had been clinically diagnosed with autism before the age of 13, the symptom score for autism decreased on average 30% over more than a decade in birth cohorts 1992–2002. There was an average decrease of 50% in the autism symptom score from 2004 to 2014 in individuals who were diagnosed with autism at ages 7–12, but there was no decrease in those diagnosed at ages 0–6. Conclusions Over time, considerably fewer autism symptoms seemed to be required for a clinical diagnosis of autism, at least for those diagnosed after the preschool years. The findings add support for the notion that the observed increase in autism diagnoses is, at least partly, the by‐product of changes in clinical practice, and flag up the need for working in agreement with best practice guidelines.