However their usefulness as tools for diagnosis is limited as no single gene predicts ADHD. ASD shows genetic overlap with ADHD at both common and rare levels of genetic variation. Environment
In addition to genetics, some environmental factors might play a role in causing ADHD. Alcohol intake during pregnancy can cause fetal alcohol spectrum disorders which can include ADHD or symptoms like it. Children exposed to certain toxic substances, such as lead or polychlorinated biphenyls, may develop problems which resemble ADHD. Exposure to the organophosphate insecticides chlorpyrifos and dialkyl phosphate is associated with an increased risk; however, the evidence is not conclusive. Exposure to tobacco smoke during pregnancy can cause problems with central nervous system development and can increase the risk of ADHD. Nicotine exposure during pregnancy may be an environmental risk.Extreme premature birth, very low birth weight, and extreme neglect, abuse, or social deprivation also increase the risk as do certain infections during pregnancy, at birth, and in early childhood. These infections include, among others, various viruses (measles, varicella zoster encephalitis, rubella, enterovirus 71). At least 30% of children with a traumatic brain injury later develop ADHD and about 5% of cases are due to brain damage.Some studies suggest that in a small number of children, artificial food dyes or preservatives may be associated with an increased prevalence of ADHD or ADHD-like symptoms, but the evidence is weak and may only apply to children with food sensitivities. The European Union has put in place regulatory measures based on these concerns.
Today, Alcon has operations in 75 countries and its products are sold in over 180 countries. Nestlé conducted an initial public offering of 25% of its stake in Alcon in 2002. The stock is traded under the ticker symbol ALC. In July 2008, Novartis purchased approximately 25% of Nestlés stake in Alcon, with an option to buy Nestlés remaining shares beginning in 2010. Novartis bought 52% stake from Nestlé for $28.1 Billion. This deal brought the total ownership of Alcon by Novartis to 77%. Beginning January 2010 Novartis formally announced it will be completing the exercise options for finishing purchasing the rest of Alcon and then promptly continue to exercise merger and takeover of Alcon.On March 29, 2010, Alcon acquired Durezol and Zyclorin from Sirion Therapeutics. Alcon received regulatory approval to acquire the rights of Durezol emulsion in the US and the global rights, excluding Latin America, for Zyclorin from Sirion Therapeutics.On June 28, 2010, Alcons Independent Director Committee announced that a recommendation by the committee was an indispensable first step before the board of the company can decide on the merger proposal of Novartis AG, refuted Novartis’ public implications that it would be able to unilaterally impose the merger irrespective of the Independent Director Committees position once Novartis became Alcons majority shareholder. On July 8, 2010, Alcons independent director committee (IDC) had set up a $50 million litigation trust to ensure companys minority shareholders get the best deal from bidder Novartis AG.On April 9, 2019, Alcon completed a 100% spin-off from Novartis.