Reports of<unk>  cases per 1,000 children rose considerably in the US from 1996 to 2007. It is unknown how much growth came from changes in rates of<unk> . As of 2007, reviews estimate a prevalence of 1–2 per 1,000 for<unk>  and close to 6 per 1,000 for ASD. A 2016 survey in the United States reported a rate of 25 per 1,000 children for ASD. Globally,<unk>  affects an estimated 24.8 million people , while Asperger syndrome affects a further 37.2 million. In 2012, the NHS estimated that the overall prevalence of<unk>  among adults aged 18 years and over in the UK was 1.1%. Rates of PDD-NOS's has been estimated at 3.7 per 1,000, Asperger syndrome at roughly 0.6 per 1,000, and childhood disintegrative disorder at 0.02 per 1,000. CDC estimates about 1 out of 59 (1.7%) for 2014, an increase from 1 out of every 68 children (1.5%) for 2010. In the UK, from 1998 to 2018, the<unk>  diagnoses increased by 787%. This increase is largely attributable to changes in diagnostic practices, referral patterns, availability of services, age at diagnosis, and public awareness (particularly among women), though unidentified environmental risk factors cannot be ruled out. The available evidence does not rule out the possibility that<unk> 's true prevalence has increased; a real increase would suggest directing more attention and funding toward psychosocial factors and changing environmental factors instead of continuing to focus on genetics. It has been established that vaccination is not a risk factor for<unk>  and is not behind any increase in<unk>  prevalence rates, if any change in the rate of<unk>  exists at all. Males are at higher risk for ASD than females. The sex ratio averages 4.3:1 and is greatly modified by cognitive impairment: it may be close to 2:1 with intellectual disability and more than 5.5:1 without. Several theories about the higher prevalence in males have been investigated, but the cause of the difference is unconfirmed; Although the evidence does not implicate any single pregnancy-related risk factor as a cause of<unk> , the risk of<unk>  is associated with advanced age in either parent, and with diabetes, bleeding, and use of psychiatric drugs in the mother during pregnancy. The risk is greater with older fathers than with older mothers; two potential explanations are the known increase in mutation burden in older sperm, and the hypothesis that men marry later if they carry genetic liability and show some signs of<unk> . Most professionals believe that race, ethnicity, and socioeconomic background do not affect the occurrence of<unk> . Several other conditions are common in children with<unk> . They include: * Genetic disorders. About 10–15% of<unk>  cases have an identifiable Mendelian (single-gene) condition, chromosome abnormality, or other genetic syndrome, and ASD is associated with several genetic disorders. * Intellectual disability. The percentage of<unk> ic individuals who also meet criteria for intellectual disability has been reported as anywhere from 25% to 70%, a wide variation illustrating the difficulty of assessing intelligence of individuals on the<unk>  spectrum. In comparison, for PDD-NOS the association with intellectual disability is much weaker, and by definition, the diagnosis of Asperger's excludes intellectual disability. * Anxiety disorders are common among children with ASD; there are no firm data, but studies have reported prevalences ranging from 11% to 84%. Many anxiety disorders have symptoms that are better explained by ASD itself, or are hard to distinguish from ASD's symptoms. * Epilepsy, with variations in risk of epilepsy due to age, cognitive level, and type of language disorder. * Several metabolic defects, such as phenylketonuria, are associated with<unk> ic symptoms. * Minor physical anomalies are significantly increased in the<unk> ic population. * Preempted diagnoses. Although the DSM-IV rules out the concurrent diagnosis of many other conditions along with<unk> , the full criteria for Attention deficit hyperactivity disorder (ADHD), Tourette syndrome, and other of these conditions are often present and these co-occurrent conditions are increasingly accepted. * Sleep problems affect about two-thirds of individuals with ASD at some point in childhood. These most commonly include symptoms of insomnia such as difficulty in falling asleep, frequent nocturnal awakenings, and early morning awakenings. Sleep problems are associated with difficult behaviors and family stress, and are often a focus of clinical attention over and above the primary ASD diagnosis.
Autism
Schizophrenia
Tourettism
Reactive attachment disorder
Puberphonia
Intellectual disability
Selective mutism
Lesch–Nyhan syndrome