The rising diagnosis rate of ADHD and autism among children may not reflect an actual increase in incidence. A recent study from the University of Copenhagen indicated that shifting diagnostic criteria and practices could be contributing Really, as a sample of contemporary diagnosed children showed comparable genetic risk profiles to children diagnosed decades ago but were on average carrying marginally less genetic risk.
The authors studied genetic data of over 37,000 individuals in Denmark who were diagnosed with either ADHD or autism spectrum disorder between 1994 and 2016. They found that individuals diagnosed in more recent years had lower mean polygenic risk scores than individuals diagnosed in earlier years. This was around 10 to 15% for ADHD diagnoses and up to 25% for autism diagnoses.
Authors suggest that this pattern can be interpreted as current diagnostic systems identifying a wider demographic. In prior decades people with more salient problems probably would have been diagnosed, and as awareness has increased and diagnostic criteria have changed then people with less obvious problems or milder syndromes can be identified.
This distinction is crucial, as genetic risk for ADHD and autism seems very heritable, but the populations genetic composition does not alter dramatically over the space of only a few decades and, because of this, the researchers from the University of Copenhagen took this into account by using genetic data as one way of investigating whether the rise in diagnoses could be attributed to a change in the type of children being diagnosed or whether it was more likely to be due to a cultural instead of a biological change of the population.
Results are consistent with a larger literature demonstrating how conceptions of autism and ADHD over time have evolved. Previous research and clinical awareness usually centered on children displaying more observable behavioral features, in particular boys. Increased awareness has enabled doctors and other clinician to recognize clinical presentations that may have previously been missed, even in girls and those with more subtle symptoms.
Other studies have also shown the potential for comorbidity. A study of over 50,000 autistic individuals discovered that those children with co-morbidpsychiatricconditions includingADHdianotstriagnosed autism any earlier than children with no co-morbidconditions. In two samples the age of diagnosis of autism increased as the number of co-morbid conditons increased.
This can but imply that increased diagnosis rates should not constantly be used as an argument for the argument that children today are fundamentally different from children from previous generations. The increased diagnosis rate could in part reflect a better recognition of existing alreadythey were present but un-diagnosed.
Both researchers and health organizations state that diagnosis is not exclusively determined by biology. Factors like availability of and access to health care, parental and professional awareness and knowledge of autism as well as diagnostic criteria and social attitudes all ‘play a role in whether and when a child is assessed’. The OECD has stated that ‘this increase in diagnoses over the last decade… appears to be partly attributable to a shift in diagnostic criteria, as well as rising awareness and decreasing stigma, throughout the community’.