The Genetics of Neurodevelopmental Disorders PDF Free Download
The term “neurodevelopmental disorders” is clinically defined in psychiatry as “a group of conditions with onset in the developmental period… characterized by developmental deficits that produce impairments of personal, social, academic, or occupational functioning”.1 This term encompasses the clinical categories of intellectual disability (ID), developmental delay (DD), autism spectrum disorders (ASD), attention-deficit hyperactivity disorder (ADHD), speech and language disorders, specific learning disorders, tic disorders, and others. However, the term can be defined differently, not based on age of onset or clinical presentation, but by an etiological criterion, to mean disorders arising from aberrant neural development. This definition includes many forms of epilepsy (considered either as a distinct disorder or as a comorbid symptom) as well as disorders such as schizophrenia (SZ), which have later onset but which can still be traced back to neurodevelopmental origins.
Though the symptoms of SZ itself typically arise only in late teens or early twenties, convergent evidence of epidemiological risk factors during fetal development and very early deficits apparent in longitudinal studies strongly indicate that SZ is a disorder of neural development, though its clinical consequences may remain latent for many years. Collectively, severe neurodevelopmental disorders affect ∼5% of the population (though exact numbers are almost impossible to obtain, due to changing diagnostic criteria and substantial comorbidity between clinical categories). These disorders impact on the most fundamental aspects of human experience: cognition, language, social interaction, perception, mood, motor control, and sense of self. They impair function, often severely, and restrict opportunities for sufferers, as well as placing a heavy burden on families and caregivers. As lifelong illnesses, they also give rise to a substantial economic burden, both in direct health-care costs and indirect costs due to lost opportunity. The treatments currently available for neurodevelopmental disorders are very limited and problematic. Intensive educational interventions may help ameliorate some cognitive or behavioral difficulties, such as those associated with ID or ASD, but to a limited extent and without addressing the underlying pathology. With respect to psychiatric symptoms, the mainstays of pharmacotherapy (antipsychotic medication, mood stabilizers, antidepressants, and anxiolytics) all emerged between the 1940s and 1960s
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