also been shown to cluster in urban neighborhoods of high socioeconomic status. One study from California found a three to fourfold increased risk of autism in a small 30 by 40 km region centered on West Hollywood, Los Angeles. Gender differences Boys have a higher chance of being diagnosed with autism than girls. The ASD 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. Recent studies have found no association with socioeconomic status, and have reported inconsistent results about associations with race or ethnicity. RORA deficiency may explain some of the difference in frequency between males and females. RORA protein levels are higher in the brains of typically developing females compared to typically developing males, providing females with a buffer against RORA deficiency. This is known as the Female protective effect. RORA deficiency has previously been proposed as one factor that may make males more vulnerable to autism. There is a statistically notable overlap between ASD populations and gender diverse populations. Comorbid conditions Autism is associated with several other conditions: Genetic disorders. About 10–15% of autism 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 fraction of autistic 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 autistic intelligence. Anxiety disorders are common among children with ASD, although there are no firm data. Symptoms include generalized anxiety and separation anxiety, and are likely affected by age, level of cognitive functioning, degree of social impairment, and ASD-specific difficulties. Many anxiety disorders, such as social phobia, are not commonly diagnosed in people with ASD because such symptoms are better explained by ASD itself, and it is often difficult to tell whether symptoms such as compulsive checking are part of ASD or a co-occurring anxiety problem. The prevalence of anxiety disorders in children with ASD has been reported to be anywhere between 11% and 84%. Epilepsy, with variations in risk of epilepsy due to age, cognitive level, and type of language disorder; 5–38% of children with autism have comorbid epilepsy, and only 16% of these have remission in adulthood. Several metabolic defects, such as phenylketonuria, are associated with autistic symptoms. Minor physical anomalies are significantly increased