Autism Spectrum Disorders

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Epidemiology

• Prevalence of autism spectrum disorders (ASDs) is roughly 1 in 100 (63-116 per 10,000).
• The prevalence of mental retardation in idiopathic autism is ~60%; when the autism spectrum is taken as a whole, prevalence of MR is 30%.
• Epilepsy has long been associated with autism, but estimates of prevalence of seizure disorder vary from 5% to 44%.

Risk Factors

• Taking SSRI's during pregnancy and up to 3 months before conception (up to 1 year before delivery) doubles the risk of ASD in the offspring; risk is even higher (adjusted OR=3.8) if the expecting mother is taking SSRIs during the first trimester. (1)
  
• Advanced maternal age is associated with increased risk in autism (SandinS, JAACAP 2012) In this metaanalysis of 16 studies, relative risk (RR) of having a child with ASD was decreased (0.76) in younger women (<20 y.o. vs. 25-29) and increased (RR=1.31) in women >35y.o.
• Advanced paternal age is likewise a risk factor. In large Swedish study, risk increased two-fold for fathers >49yo, and four-fold for fathers 55 and older;(3) meta-analysis of 12 studies (presented in the same study) corroborated those findings.

Neuroanatomy (2)

An autistic brain undergoes a period of precocious growth during early postnatal life (1st year of life through early childhood) followed by a deceleration in age-related growth, based on head circumference and MRI studies.

• Abnormal brain enlargement in children with autism is disproportionately accounted for by increased white matter.
• Precocious enlargement in amygdala begins early and persist into late childhood; it does not undergo normal growth spurt in latency and adolescence. Adult autistic patients may have normal or decreased size amygdala.

Screening

M-CHAT: screen children for PDD as young as 18mo.

Psychopharmocology

• Risperdone has FDA indicaiton for use in children with ASD
• Cochrane review of aripiprazole (Abilify) for ASD found it to be effective in decreassing irritability, hyperactivity, and stereotypies. Notable side effects were weight gain, sedation, drooling, and EPS. (2012)

References

(1) Croen LA, Grether JK, Yoshida CK, Odouli R, Hendrick V. Antidepressant use during pregnancy and childhood autism spectrum disorders. Arch Gen Psychiatry. 2011;68(11):1104-1112.
(2) Amaral et. al. Neuroanatomy of Autism. Trends in Neurosciences 2008 31(3):137-145.
(3) Hultman et. al. Advancing paternal age and risk of autism: new evidence from a population-based study and a meta-analysis of epidemiological studies. Molecular Psychiatry (2011) 16, 1203-1212.