<unk>  can affect<unk>  in various ways. Conversely,<unk>  can affect<unk> .<unk>  effects on<unk>  have been described as being among the most important factors in the origins of human group differences in IQ test scores and other measures of cognitive ability. Several factors can lead to significant cognitive impairment, particularly if they occur during pregnancy and childhood when the brain is growing and the blood–brain barrier of the child is less effective. Such impairment may sometimes be permanent, sometimes be partially or wholly compensated for by later growth. Developed nations have implemented several<unk>  policies regarding nutrients and toxins known to influence cognitive function. These include laws requiring fortification of certain food products and laws establishing safe levels of pollutants (e.g. lead, mercury, and organochlorides). Comprehensive policy recommendations targeting reduction of cognitive impairment in children have been proposed. Improvements in nutrition (often involving specific micronutrients) due to public policy changes have been implicated in IQ increases in many nations (as part of the overall Flynn effect), such as efforts fighting iodine deficiency in the U.S.
Impact of health on intelligence
Biology of depression
Effects of domestic violence on children
Impact of alcohol on aging
Psychological effects of Internet use
Genetics of post-traumatic stress disorder
Heritability of autism
Mechanism of autism