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The Teen Brain:Primed to Learn, Primed to Take RisksBy Jay N. Giedd, M.D.During adolescence the brain’s ability to change isespecially pronounced—and that can be a double-edgedsword. Jay N. Giedd, a child and adolescent psychiatristat the National Institute of Mental Health who specializesin brain imaging, points out that the brain’s plasticityallows adolescents to learn and adapt, which paves theway for independence. But it also poses dangers:different rates of development can lead to poor decisionmaking, risk taking—and, in some cases, diagnosabledisorders.Across cultures and millennia, the teen years have beennoted as a time of dramatic changes in body andbehaviour. During this time most people successfullynavigate the transition from depending upon family tobecoming a self-sufficient adult member of the society.However, adolescence is also a time of increasedconflicts with parents, mood volatility, risky behaviourand, for some, the emergence of psychopathology.The physical changes associated with puberty areconspicuous and well described. The brain’stransformation is every bit as dramatic but, to theunaided eye, is visible only in terms of new and differentbehaviour. The teen brain is not broken or defective.Rather, it is wonderfully optimised to promote oursuccess as a species.Beginning in childhood and continuing throughadolescence, dynamic processes drive braindevelopment, creating the flexibility that allows the brainto refine itself, specialize and sharpen its functions forthe specific demands of its environment. Maturingconnections pave the way for increased communicationamong brain regions, enabling greater integration andcomplexity of thought. When what we call adolescencearrives, a changing balance between brain systemsinvolved in emotion and regulating emotionspawns increased novelty seeking, risk taking and a shifttoward peer-based interactions.These behaviours, found in all social mammals,encourage separating from the comfort and safety of ourfamilies to explore new environments and seekunrelated mates. 1 However, these potentially adaptivebehaviours also pose substantial dangers, especiallywhen mixed with modern temptations and easy accessto potent substances of abuse, firearms and high-speedmotor vehicles.In many ways adolescence is the healthiest time of life.The immune system, resistance to cancer, tolerance forheat and cold and several other variables are at theirpeak. Despite physical strengths, however, illness andmortality increase 200 percent to 300 percent. As of2005, the most recent year for which statistics areavailable, motor vehicle accidents, the No. 1 cause,accounted for about half of deaths. Nos. 2 and 3 werehomicide and suicide. 2 Understanding this healthy-body,risk-taking-brain paradox will require greater insight intohow the brain changes during this period of life. Suchenhanced understanding may help to guide interventionswhen illnesses emerge or to inform parenting oreducational approaches to encourage healthydevelopment.Different parts of the brain mature at varying rates duringadolescence. This image indicates an average decrease ingrey matter volumes between ages 5 and 20, thanks tothe pruning of neural connections. Areas that mediate“executive functioning” mature later than areasresponsible for basic functions. (Image courtesy of Jay N.Giedd, M.D.)Adolescent Neurobiology: Three ThemesThe brain, the most protected organ of the body, hasbeen particularly opaque to investigation of what occursduring adolescence. But now the picture emerging fromthe science of adolescent neurobiology highlights boththe brain’s capacity to handle increasing cognitivecomplexity and an enormous potential for plasticity—thebrain’s ongoing ability to change. The advent ofstructural and functional magnetic resonance imaging(MRI), which combines a powerful magnet, radio waves,and sophisticated computer technology to provideexquisitely accurate pictures of brain anatomy andphysiology, has opened an unprecedented window intothe biology of the brain, including how its tissuesfunction and how particular mental or physical activitieschange blood flow. Because the technique does not useionising radiation, it is well suited for pediatric studiesand has launched a new era of neuroscience. Threethemes emerge from neuroimaging research inadolescents:January 2013 6Serial No 15