Autism and autism spectrum disorders are complex neurodevelopmental disorders. Many causes of autism have been proposed, but its theory of causation is still incomplete.  Heritability contributes about 90% of the risk of a child developing autism, but the genetics of autism are complex and typically it is unclear which genes are responsible.  In rare cases, autism is strongly associated with agents that cause birth defects.  Many other causes have been proposed, such as exposure of children to vaccines; these proposals are controversial and the vaccine hypotheses have no convincing scientific evidence. 4] Autism is a condition involving abnormalities of brain development and behavior which manifests itself before a child is three years old and has a steady course with no remission.
It is characterized by impairments in social interaction and communication, as well as restricted and repetitive behavior. It is part of a larger family called the autism spectrum disorders (ASD) or pervasive developmental disorders (PDD), which include closely related syndromes such as Asperger syndrome and PDD-NOS. 5] This article uses autism to denote the classic autistic disorder and ASD to denote the wider family. Autism’s theory of causation is still incomplete.  There is increasing suspicion among researchers that autism does not have a single cause, but is instead a complex disorder with a triad of core aspects (social impairment, communication difficulties, and repetitive behaviors) that have distinct causes but often co-occur. 7] The number of people known to have autism has increased dramatically since the 1980s, at least partly due to changes in diagnostic practice; it is unknown whether prevalence has increased as well.  An increase in prevalence would suggest directing more attention and funding toward changing environmental factors instead of continuing to focus on genetics. The diagnosis of epilepsy requires that the seizures be unprovoked, with the implication that the provocant is assumed to be something obviously harmful.
However, in some epilepsy syndromes, the provocant can reasonably be considered to be part of normal daily life. Examples of these normal provocants include reading, hot water on the head, hyperventilation, and flashing or flickering lights. This last provocant is a special type of reflex epilepsy called photosensitive epilepsy. Although it is commonly assumed that photosensitivity is a common element to all epilepsies, among both patients and the public, only around 3% of people with epilepsy are affected by flickering lights.
Certain environmental factors can lead to an increased likelihood of seizures in someone with epilepsy or in certain syndromes, for example: •being asleep •the transition between sleep and wakefulness (hypnogogia) •tiredness and sleep deprivation •illness •constipation •menstruation •stress or anxiety •alcohol consumption •very severe depression and bipolar disorders[cita Epilepsy is a common chronic neurological disorder that is characterized by recurrent unprovoked seizures.  These seizures are transient signs and/or symptoms due to abnormal, excessive or synchronous neuronal activity in the brain. 3] About 50 million people worldwide have epilepsy at any one time.  Epilepsy is usually controlled, but not cured, with medication, although surgery may be considered in difficult cases. Not all epilepsy syndromes are lifelong – some forms are confined to particular stages of childhood. Epilepsy should not be understood as a single disorder, but rather as a group of syndromes with vastly divergent symptoms but all involving episodic abnormal electrical activity in the brain.