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disorders strike 44 million adults a year at a cost of $148 billion. Advances in research could reduce these costs. For example, discovering how to delay the onset of Alzheimer’s disease by five years could save $50 billion in annual health care costs. In the past two decades, neuroscience has made impressive progress in many of the field’s key areas. Now, more than ever, neuroscience is on the cusp of major breakthroughs. Recently, significant findings have been documented in the following areas. Genetics Disease genes have been identified that are key to several disorders, including the epilepsies, Alzheimer’s disease, Huntington’s disease, Parkinson’s disease, and amyotrophic lateral sclerosis (ALS). These discoveries have provided new insight into underlying disease mechanisms and are beginning to suggest new treatments. With the mapping of the human genome, neuroscientists have been able to make more rapid progress in identifying genes that either contribute to or directly cause human neurological disease. Mapping animal genomes has aided the search for genes that regulate and control many complex behaviors. Gene-environment Interactions Most major diseases have a genetic basis strongly influenced by the environment. For example, identical twins, who share the same DNA, have an increased risk of getting the same disease compared with nonidentical siblings. However, if one twin gets the disease, the probability the other will also be affected is between 30 percent and 60 percent, indicating that there are environmental factors at play as well. Environmental influences involve factors such as exposure to toxic substances, diet, level of physical activity, and stressful life events.
