We explore how the brain forms, develops and matures, and how alterations in these processes can cause neurodevelopmental disorders. Led by a multidisciplinary team of scientists, pediatricians, neurologists, and psychiatrists, at the MRC Centre for Neurodevelopmental Disorders we believe that unlocking the mysteries of the developing brain will allow us to identify new treatments that improve the lives of affected individuals and their families.
The human brain develops over two decades, a substantial part of our life. During that time, the brain grows from a microscopic structure to a remarkable organ that enables us to interact with the physical world, communicate, learn and imagine the unknown. In some circumstances, however, brain development may deviate from its typical programme and cause a disorder.
Neurodevelopmental disorders are a group of conditions that are caused by an alteration in the development of the nervous system. Intellectual disabilities, autism spectrum conditions and many forms of epilepsy are caused by diversions in the normal programme of brain development. Even psychosis and related disorders, which emerge later in life, are thought to have a developmental origin.
There is some disparity between what is classified as a neurodevelopmental disorder by researchers and which clinical diagnoses fall under the umbrella term, neurodevelopmental disorders. neurodevelopmental disorder diagnoses are listed in the Diagnostic and Statistical Manual 5 (DSM-5) and the International Classification of Diseases 11 (ICD-11). Both list six broad categories comprising developmental intellectual disabilities, communication disorders, autism spectrum disorders (ASD), attention deficit hyperactivity disorder (ADHD), neurodevelopmental motor disorders and other learning disorders. Researchers typically use a broad definition of neurodevelopmental disorders and include other conditions resulting from differences in the way the nervous system develops and leading to differences in emotion, communication skills, cognition, and behaviour. Recent research has shown that some conditions that only usually appear in adult life, such as schizophrenia, have neurodevelopmental origins.
Figures from 2012 estimate that neurodevelopmental disorders affect approximately 3-4% of children in the United Kingdom with ADHD and autism spectrum conditions being the most common diagnoses, accounting for approximately 75% of neurodevelopmental disorder diagnoses. Schizophrenia and epilepsy are less common. The World Health Organization states that schizophrenia affects 0.32% of adults worldwide. Epilepsy affects 0.5 – 1% of children and seizure characteristics in children can be quite different to those observed in adults.
Developmental brain disorders arise through a combination of genetic and environmental (non-genetic) influences.
Research over the past decade has shown that genetic changes are the most important risk factor for developmental brain disorders, independently of whether they manifest early in life, such as autism spectrum conditions or only become clinically detectable in young adults, such as psychosis. This does not mean that these conditions always run in families, because sometimes the genetic changes that increase the risk of developmental brain disorders occur in the reproductive cells of one of the parents and so the disease arises sporadically in the next generation without having been present in the family before.
Gene changes increase the risk that a child develops a brain disorder, but some gene alterations associated with a developmental condition can also be found in people who don’t have the disorder. And, in some cases, changes in the same gene are found in patients with different clinical outcomes. This is most likely due to differences in other genes (which may provide resilience to a particular disease) or exposure to environmental risk factors. For example, research shows that severely premature babies are more likely to develop a brain disorder later in life than babies that are born at term.
Neurodevelopmental disorders are diagnosed by a clinical practitioner or another qualified person. The practitioner will assess and evaluate a child for symptoms and behaviours that are characteristic of neurodevelopmental disorders (for example, communication, cognition and functional skills). These assessments take the whole child into account and will review the child’s strengths as well as any weaknesses to gather an accurate developmental picture. Assessments are normally scheduled after a parent, guardian or teacher raises concerns with a clinician.
Suspected neurodevelopmental disorders can sometimes be confirmed with genetic testing (depending on the diagnosis suspected). Traditionally, karyotype analysis is used to detect genetic and chromosomal differences. More recently, advances in our understanding and the development of novel genetic methods mean that in some cases, more detailed genetic analyses can be performed.
Diagnosis of a neurodevelopmental disorder will normally require more than one appointment, and it may be necessary to meet different practitioners with different expertise (for example, paediatricians, clinical psychologists, occupational therapists and speech and language therapists). Sessions usually comprise a mixture of formal and play-based assessments with the child, as well as information gathering from the parent(s) or guardian(s). The practitioners will normally meet following the assessments to discuss the child before feeding back to the parent(s) or guardian(s).