Furthermore, neuroscience is at the frontier of investigation of the brain and mind. The study of the brain is becoming the cornerstone in understanding how we perceive and interact with the external world and, in particular, how human experience and human biology influence each other. It is likely that the study of the brain will become one of the central intellectual endeavors in the coming decades.
Major depressive disorder (also known as clinical depression, major depression, unipolar depression, or unipolar disorder) is a mental disorder typically characterized by a pervasive low mood, low self-esteem, and loss of interest or pleasure in usual activities. The term was selected by the American Psychiatric Association for the 1980 version of the Diagnostic and Statistical Manual of Mental Disorders (DSM-III) classification for the symptom cluster, and has become widely used since. The general term depression is often used to describe the disorder, but since it is also used to describe temporary sadness or a depressed mood, more precise terminology is preferred in clinical use and research. Major depression is an often disabling condition which adversely affects a person's family, work or school life, sleeping and eating habits, and general health. In the United States around 3.4% of people with major depression commit suicide, and up to 60% of all people who commit suicide have depression or another mood disorder.
The diagnosis of major depressive disorder is based on the patient's self-reported experiences, behavior reported by relatives or friends, and mental state. There is no laboratory test for major depression, although physicians generally request tests for physical conditions that may cause similar symptoms. The most common time of onset is between the ages of 30 and 40 years, with a later peak between 50 and 60 years. Major depression occurs about twice as frequently in women as in men, although men are at higher risk for suicide.
Most patients are treated in the community with antidepressant medication and supportive counseling, and some with psychotherapy. Admission to hospital may be necessary in cases associated with self-neglect or a significant risk of harm to self or others. A minority with severe illness may be treated with electroconvulsive therapy (ECT), under a short-acting general anaesthetic. The course of the disorder varies widely, from a once-only occurrence lasting months to a lifelong disorder with recurrent major depressive episodes. Depressed individuals have a shorter life expectancy than those without depression, being more susceptible to medical conditions such as heart disease. Sufferers and former patients may be stigmatized.
The understanding of the nature and causes of depression has evolved over the centuries; nevertheless, many aspects of depression are still not fully understood, and are the subject of debate and research. Psychological, psycho-social, evolutionary and biological causes have been proposed. Psychological treatments are based on theories about personality, interpersonal communication, and unduly negative thoughts. The monoamine chemicals serotonin, norepinephrine, and dopamine are naturally present in the brain and assist communication between nerve cells. Monoamines have been implicated in depression, and most antidepressants work to increase the active levels of at least one.
Addiction:An international team of scientists have found that the drug (+)-naloxone may be able to combat the addictive effects of opioids. By binding to the body's TLR4 immune receptors, substances like heroin no longer produce the dopamine needed to generate substance dependence yet retains the pain-relieving effect of these drugs. This means that if both morphine and (+)-naloxone are taken simultaneously, a patient will receive the necessary analgesic effect of the morphine but avoid the potential for addiction. The team hopes to soon begin clinical testing of this promising application. .
Neurodegenerative Disease Based on a study involving primates, scientists may soon be able to employ genetic engineering to treat such devastating human diseases as Alzheimer's disease and Parkinson's. Studies reveal that a substance called human nerve growth factor, a naturally occurring protein, has beneficial effects on brain cells. When genetically engineered growth factor-producing cells were injected into the brains of monkeys, deterioration was reversed in up to 92 percent of diseased brain cells. 
Memory: A team of researchers led by Itzhak Fried, recording from electrodes implanted in the brains of human epileptic patients, found many neurons in the hippocampus that were activated both while viewing specific parts of video clips, and while recollecting the same episodes that activated them during viewing.
Fibromyalgia: This chronic pain condition has been so difficult to study that some physicians have doubted that it really exists. A study published in the November issue of the Journal of Nuclear Medicine used SPECT imaging to examine brain activity of fibromyalgia sufferers with controls, and found that the patients showed enhanced blood flow in regions involved in discriminating pain, together with reduced blood flow in other regions. This supports other recent findings of measurable neural differences in fibromyalgia patients.
Placebo: For many conditions, pharmacologically inactive treatments such as sugar pills may have effects in some people comparable to those of more potent treatments. A study by a group of Swedish researchers, published in the Journal of Neuroscience, shows that genetic factors may at least partly underlie individual differences in the effectiveness of placebo. People with specific variants of the serotonin transporter gene or the dopamine hydroxylase gene showed greater anxiety-reduction responses to a placebo treatment than people with other variants.