Media Releases

Study finds new ADHD genes, links susceptibility with autism and other neuropsychiatric conditions

August 9, 2011

TORONTO, ON – New research led by The Hos­pi­tal for Sick Chil­dren (Sick­Kids) and the Uni­ver­si­ty of Toron­to has iden­ti­fied more genes in atten­tion deficit hyper­ac­tiv­i­ty dis­or­der (ADHD) and shows that there is an over­lap between some of these genes and those found in oth­er neu­ropsy­chi­atric con­di­tions such as autism spec­trum dis­or­der (ASD). The study is pub­lished in the August 10 advance online edi­tion of Sci­ence Trans­la­tion­al Med­i­cine.

The research team was led by Dr. Rus­sell Schachar, Senior Sci­en­tist and Psy­chi­a­trist at Sick­Kids and Pro­fes­sor of Psy­chi­a­try at the Uni­ver­si­ty of Toron­to, and Dr. Stephen Scher­er, Senior Sci­en­tist at Sick­Kids, Direc­tor of The Cen­tre for Applied Genomics at Sick­Kids and the McLaugh­lin Cen­tre at the Uni­ver­si­ty of Toron­to.

The sci­en­tists used microar­rays (gene-chip tech­nol­o­gy) to study the DNA of 248 unre­lat­ed patients with ADHD. They specif­i­cal­ly searched for copy num­ber vari­ants (CNVs), which are inser­tions or dele­tions affect­ing the genes. In three of 173 chil­dren for whom the DNA of both par­ents was avail­able, they found spon­ta­neous CNVs, which occur when the par­ents are not affect­ed and muta­tions are new to the child. Rare CNVs that were inher­it­ed from affect­ed par­ents were found in 19 of 248 patients.

With­in the group of inher­it­ed CNVs, the researchers found some of the genes that had pre­vi­ous­ly been iden­ti­fied in oth­er neu­ropsy­chi­atric con­di­tions includ­ing ASD. To explore this over­lap, they test­ed a dif­fer­ent group for CNVs. They found that nine of the 349 chil­dren in the study, all of whom had pre­vi­ous­ly been diag­nosed with ASD, car­ried CNVs that are relat­ed to ADHD and oth­er dis­or­ders.

The find­ings sug­gest that some CNVs, which play a causal role in ADHD, demon­strate com­mon sus­cep­ti­bil­i­ty genes in ADHD, ASD and oth­er neu­ropsy­chi­atric dis­or­ders.

“For the first time, we’ve test­ed these genet­ic alter­ations in ADHD and have a pret­ty good han­dle on a cou­ple of decent ADHD can­di­date genes,” says Scher­er, who is also Pro­fes­sor in the Depart­ment of Mol­e­c­u­lar Genet­ics at the Uni­ver­si­ty of Toron­to and Glax­o­SmithK­line Chair in Genome Sci­ences at Sick­Kids. “This is crit­i­cal, as it gives us con­fi­dence in inter­pret­ing our results.”

Like ASD, ADHD cas­es are large­ly unique, notes Schachar, who is also the TD Chair in Child and Ado­les­cent Psy­chi­a­try at Sick­Kids. Peo­ple car­ry­ing the same CNVs can have dif­fer­ent symp­toms, he says. “It’s not always the same risk. As we’ve seen in autism and oth­er con­di­tions, rel­a­tive­ly few of these CNVs repeat in affect­ed indi­vid­u­als.”

Most indi­vid­u­als with ADHD also have at least one oth­er con­di­tion, such as anx­i­ety, mood, con­duct or lan­guage dis­or­ders. Up to 75 per cent of peo­ple with ASD also have atten­tion deficits or hyper­ac­tiv­i­ty. “A lot of these asso­ci­at­ed prob­lems prob­a­bly arise from the fact that they are shar­ing genet­ic risk for dif­fer­ent con­di­tions,” says Schachar.

The research results could be reas­sur­ing for clin­i­cians who may see char­ac­ter­is­tics of dif­fer­ent neu­ropsy­chi­atric con­di­tions in their patients – such as ASD-like social prob­lems in a child with ADHD – but are con­cerned that they are over-inter­pret­ing these traits. “This research rein­forces the notion that their gut obser­va­tion is cor­rect,” Schachar says.

Accord­ing to Scher­er, the his­tor­i­cal mind­set in research has been to define the spe­cif­ic clin­i­cal syn­drome and explore it. “Researchers don’t tend to look across dis­or­ders very often. This method is per­haps one of the most excit­ing find­ings in neu­ropsy­chi­atric genet­ics and it is real­ly start­ing to rede­fine how we think about neu­ropsy­chi­atric con­di­tions,” he says.

“These are prob­a­bly genet­ic fac­tors that increase the risk for var­i­ous kinds of neu­ropsy­chi­atric dis­or­ders and it pos­es a huge chal­lenge to us to fig­ure out what makes an ADHD case, what makes an ASD case. There are lots of dif­fer­ent pos­si­bil­i­ties to explain why some com­mon risks can man­i­fest into dif­fer­ent kinds of dis­or­ders,” Schachar says, adding that while the new study observed this phe­nom­e­non, more research is need­ed to deter­mine the cause.

ADHD is a com­mon neu­ropsy­chi­atric dis­or­der that affects four per cent of school-age chil­dren world­wide. It is asso­ci­at­ed with inat­ten­tion, hyper­ac­tiv­i­ty and impul­sive­ness that often results in learn­ing dif­fi­cul­ties, social prob­lems and under­achieve­ment.

ASDs are diag­nosed in rough­ly one in 100 chil­dren in North Amer­i­ca and cause deficits in com­mu­ni­ca­tion, social under­stand­ing and behav­iour.

The study was fund­ed by The Cen­tre for Applied Genomics, Genome Cana­da, The Ontario Genomics Insti­tute, the Cana­di­an Insti­tutes of Health Research, the Cana­di­an Insti­tute for Advanced Research, the McLaugh­lin Cen­tre, the Cana­da Foun­da­tion for Inno­va­tion, the Min­istry of Research and Inno­va­tion, Neu­roDe­vNet, Autism Speaks and Sick­Kids Foun­da­tion.

About The Hos­pi­tal for Sick Chil­dren
The Hos­pi­tal for Sick Chil­dren (Sick­Kids) is rec­og­nized as one of the world’s fore­most pae­di­atric health-care insti­tu­tions and is Canada’s lead­ing cen­tre ded­i­cat­ed to advanc­ing children’s health through the inte­gra­tion of patient care, research and edu­ca­tion. Found­ed in 1875 and affil­i­at­ed with the Uni­ver­si­ty of Toron­to, Sick­Kids is one of Canada’s most research-inten­sive hos­pi­tals and has gen­er­at­ed dis­cov­er­ies that have helped chil­dren glob­al­ly.  Its mis­sion is to pro­vide the best in com­plex and spe­cial­ized fam­i­ly-cen­tred care; pio­neer sci­en­tif­ic and clin­i­cal advance­ments; share exper­tise; fos­ter an aca­d­e­m­ic envi­ron­ment that nur­tures health-care pro­fes­sion­als; and cham­pi­on an acces­si­ble, com­pre­hen­sive and sus­tain­able child health sys­tem. Sick­Kids is proud of its vision for Health­i­er Chil­dren. A Bet­ter World. For more infor­ma­tion, please vis­it

About Sick­Kids Research & Learn­ing Tow­er
Sick­Kids Research & Learn­ing Tow­er will bring togeth­er researchers from dif­fer­ent sci­en­tif­ic dis­ci­plines and a vari­ety of clin­i­cal per­spec­tives, to accel­er­ate dis­cov­er­ies, new knowl­edge and their appli­ca­tion to child health — a dif­fer­ent con­cept from tra­di­tion­al research build­ing designs.  The Tow­er will phys­i­cal­ly con­nect Sick­Kids sci­ence, dis­cov­ery and learn­ing activ­i­ties to its clin­i­cal oper­a­tions.  Designed by award-win­ning archi­tects Dia­mond + Schmitt Inc. and HDR Inc. with a goal to achieve LEED® Gold Cer­ti­fi­ca­tion for sus­tain­able design, the Tow­er will cre­ate an archi­tec­tur­al land­mark as the east­ern gate­way to Toronto’s Dis­cov­ery Dis­trict.  Sick­Kids Research & Learn­ing Tow­er is fund­ed by a grant from the Cana­da Foun­da­tion for Inno­va­tion and com­mu­ni­ty sup­port for the ongo­ing fundrais­ing cam­paign. For more infor­ma­tion, please vis­it

About the Uni­ver­si­ty of Toron­to
Estab­lished in 1827, the Uni­ver­si­ty of Toron­to has assem­bled one of the strongest research and teach­ing fac­ul­ties in North Amer­i­ca, pre­sent­ing top stu­dents at all lev­els with an intel­lec­tu­al envi­ron­ment unmatched in breadth and depth on any oth­er Cana­di­an cam­pus. U of T fac­ul­ty co-author more research arti­cles than their col­leagues at any uni­ver­si­ty in the US or Cana­da oth­er than Har­vard. As a mea­sure of impact, U of T con­sis­tent­ly ranks along­side the top five U.S. uni­ver­si­ties whose dis­cov­er­ies are most often cit­ed by oth­er researchers around the world.  The U of T fac­ul­ty are also wide­ly rec­og­nized for their teach­ing strengths and com­mit­ment to grad­u­ate super­vi­sion.



For more infor­ma­tion, please con­tact:

Suzanne Gold
The Hos­pi­tal for Sick Chil­dren
416–813-7654, ext. 2059

Paul Can­tin
Uni­ver­si­ty of Toron­to Temer­ty Temer­ty Fac­ul­ty of Med­i­cine