This article is based on key recent published literature including international guidelines and relevant reviews and meta-analyses. Authors have also supplemented this material with their own clinical experience.There is an agreement that autism spectrum disorder (ASD) have a strong hereditary component. There is also a consensus that the reported prevalence estimates have increased in the last 5 years. There is strong support for using the broader spectrum disorder conceptualization of the DSM-5.Higher public awareness of ASD has generated several controversial theories of causation. We review a number of environmental risk factors receiving media attention including: vaccines, mercury, heavy metal exposure and Selective Serotonin Uptake Inhibitors (SSRIs). Popular yet controversial treatment interventions are discussed. Early diagnostic screening tools are also addressed.There is increasing scientific interest in identifying biomarkers of autism with potential for early diagnosis, prognostic indicators and predictive treatment responses. We review evidence from genetics, neuroimaging and eye tracking as candidate biomarkers.Family studies point to a strong hereditary component in the aetiology of autism. However these studies have not established 100% concordance rates, suggesting a role for environmental factors. The gene-environment interplay has not received enough attention in scientific research. This represents an important new avenue for research in ASD.