![]() Please read the comprehensive article on the neurobiology of ADHD. NEUROSCIENCE OF AUTISM SPECTRUM DISORDER (ASD) Other possible postnatal factors include severe isolation in institutionalised children.There is unequivocally no link between the MMR vaccine and AS. ![]() Although the link is still unclear, there have been small increases in the rate of ASD in families that live near either a motorway or a farm.Toxins ranging from pesticides to car exhaust fumes to cigarette smoke have all been proposed as risk factors.The effect is suggested to be stronger during the first and second trimesters. Valproic acid and SSRIs have been implicated today.The first indication that a drug administered during pregnancy could be associated with an increased risk of autism was thalidomide.It has been proposed that circulating maternal antibodies directed against foetal brain proteins may also be a risk factor.However, the MMR vaccine has eliminated this environmental risk, and no evidence links other viral infections such as influenza.Maternal rubella has been shown to increase the risk of autism.Neurotransmitters – GABA receptor subunits (GABRB3, BAGRA5, and GABRG3) play a significant role in inhibitory transmitter receptors in the brain.Fragile X syndrome – Expansion of the CGG trinucleotide repeat (55-200 CGG repeats) in the FMR1 gene has been linked in 1-3% of children with autism.It has also been suggested to play a role in regulating the circadian clock. ![]() UBE3A is involved in the ubiquitin-proteasome pathway, which plays a role in synaptic development.It is a transcription factor that plays a role in the development of the central nervous system, particularly in the formation of serotonergic and noradrenergic nuclei in the mid and hindbrain. ENGRAILED 2 was the first gene to be proposed to increase ASD susceptibility.However, 75-80% of cases cannot be traced to a specific genetic issue, with only 20-25% of cases classified as either cytogenetically visible chromosomal abnormalities, copy number variants, or single-gene disorders. Genome-wide linkage studies have identified ASD susceptibility genes on chromosomes 2q, 7q, 15q, and 16p. There is vast genetic heterogeneity in ASD, involving both locus and allelic heterogeneity. The gene-environment interaction can affect epigenetic expressions such as DNA methylation, histone modification and microRNA expression leading to altered development.Įpigenetic Mechanisms in Psychiatric Disorders – Major Depression, Psychosis and Addiction , Īutism has a strong genetic component, with high heritability estimates of both conditions (ranging between 70 and 80% for ADHD and 37 and > 90% for ASD).Įnvironmental factors contribute to the aetiology. The commonality was also seen within molecular pathways and functional domains impacted by both disorders. In a genome-wide case-control study of psychiatric disorders (schizophrenia, bipolar disorder, major depressive disorder, autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD)), many genetic copy number variants (CNVs) were shown to confer risks for ADHD and ASD. Applications of N-Acetylcysteine (NAC) – From Addiction to Autism by Prof M Berk (March 3, 2017)ĪDHD and ASD show a shared aetiology in multiple neurobiological aspects. ![]()
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