Bipolar disorder in adolescents and children has recently become the focus of increasing study. During adolescence, normal developmental mood shifts may complicate the diagnosis of mood disorders. The commonality of symptoms associated with a variety of childhood disorders (especially ADHD) confuses the diagnostic process. Confusion regarding comorbidity can also occur if cross-sectional rather than longitudinal analyses are conducted. Genetic imprinting is the differential gene expression depending on whether the illness is transmitted maternally or paternally. Psychosocial functioning in bipolar youth has been described premorbidly and postillness onset (4.6 years) in a cohort of BMD I teenagers. Many young people who are initially diagnosed as having unipolar depression or dysthymia later meet criteria for a bipolar disorder. Electro-convulsive therapy (ECT) in adults with bipolar illness is one of the most effective treatments in both the depressive and manic phases of bipolar illness.

This chapter reviews the normal development of central nervous system (CNS), developmental aspects of neurotransmitters and receptors, developmental neuroimaging, and experimental studies involving psychotropic compounds in young animals. The complementary concepts of brain plasticity and sensitive periods are two important frameworks which inform many aspects of brain development. It is known that neurotransmitters and receptors are expressed at their highest levels in the immature brain and in anatomic regions different than in the mature brain, even in the absence of fully functional synapses. Investigators have hypothesized that stressful experiences during development may have a long-term effect on hippocampus by directly altering its structure and functioning. Two areas of research that are of immediate application in the child and adolescent age group are the theory of genetic anticipation and the identification of candidate genes in ADHD.

This chapter discusses the use of magnetic resonance spectroscopy (MRS) and functional magnetic resonance imaging (fMRI) techniques in childhood-onset anxiety disorders. It reviews brain imaging studies in various childhood-onset anxiety disorders, including obsessive-compulsive disorder (OCD), generalized anxiety disorder (GAD), panic disorder, social phobia, and post-traumatic stress disorder (PTSD), as well as suggest directions for future investigation. Functional neuroimaging has most consistently identified the caudate nucleus, ventral prefrontal cortex, and anterior cingulate as neural substrates of OCD. These regions have shown abnormal serotonergic and/or glutamatergic function. The brain regions implicated in panic disorder are consistent with the brain networks subserving fear and anxiety. The structural imaging findings suggest that functional dysfunction in the hippocampus is associated with PTSD. The studies highlight that some of the common findings in OCD and PTSD may reflect similarities in symptoms, with both disorders involving repetitive, ritualistic behaviors and intrusive thoughts.