Final answer:
Abrupt severe intellectual disability can be caused by genetic disorders like Down syndrome, environmental factors including extreme poverty, and trauma that affects brain development.
Step-by-step explanation:
The causes of abrupt severe intellectual disability include a range of factors, notably genetic disorders, significant environmental factors, and trauma. Intellectual disability, previously referred to as mental , is when an individual's intellectual and adaptive functioning is significantly below average. Genetic disorders such as Down syndrome are well-known for causing intellectual disabilities and may also bring about additional health challenges, including vision problems and congenital heart disease. Additionally, autism, which is classified under autism spectrum disorders (ASDs), can result in a variety of cognitive and behavioral impairments. Environmental factors, encompassing extreme poverty and associated stress, can negatively influence brain development, potentially leading to lowered intelligence. Lastly, trauma, particularly during critical periods of brain development, can cause cognitive disruption and contribute to developmental disorders.