Fof yours reading the words on this page, to your memory of breakfast, to the tickling of your hair against your skin, your experiences are the work of nerve cells. So are your feelings, chains of reasoning, good and less good habits. So are your anxieties, moods, and the tremors and memory lapses that, if they don’t plague you already, likely will in the long run. The entire panoply of human experience can be found in electrochemical pulses that are transmitted throughout and among the 90 billion nerve cells, also known as neurons, that make up a person’s brain.
When minds change, so do brains, and the reverse is also true. Things that change the brain and central nervous system, or the behavior of specific types of neurons and supporting cells within those structures, can also change minds, for better or for worse. When brains age, are damaged, or are diverted by recreational drugs, minds are also modified. Sometimes entire personalities change. This means that drugs and other treatments that target neurons can be used to address both physical diseases—neural degeneration, for example—and mental ones.
A hundred years ago, a single discipline of neuropsychiatry dominated the study and care of brain dysfunction. A schism emerged, starting in the thirties. Today, the departments of neurology, which deal with organic dysfunction of the nervous system, and those of psychiatry, which deal with the human mind, remain separate. Many people believe that the merger of the two is long overdue. This becomes more important as biological links to mental disorders such as depression and anxiety become apparent. Because thoughts and feelings, and therefore the way the brain is wired, have a role to play within the brain, they also play a role in disease.
The science that informs both fields is both advanced and also quite primitive. The brain is so complex that scientific understanding of it can seem decades behind that of other organs. In addition to its billions of neurons, the brain has a similar number of non-neuronal cells known as glia, which provide the insulation to keep neuronal currents separate, as well as the nutrients necessary for neurons to generate these currents and immune responses and waste. elimination services that the brain needs to stay healthy. Glial cells even help remove unwanted connections from the brain during development. The story of the role these cells play in brain health is just beginning to unfold.
Neurons talk to each other through gaps called synapses, places where a signal that has been transmitted electronically along one cell’s body is translated into a chemical message for transmission to the next. More than 100 of these neurotransmitters have been discovered so far. But while some, like serotonin and dopamine, have become household names, there’s still a lot of work to be done to understand how they and their more obscure peers work.
In the second half of the 20th century, doctors discovered a number of psychiatric drugs. But each of the three major classes of psychiatric drugs—antidepressants, antipsychotics, and anxiolytics—was discovered by chance. Scientific accounts of how they worked were absent, incomplete or incorrect. A decade ago no mechanistically new drug had reached the market in more than three decades. It was said that psychopharmacology was in crisis.
But now new ideas in neuroscience are arriving at an impressive speed. Much of this is based on genetics and a growing knowledge of molecular circuits. Other drivers of progress include tools such as optogenetics, organoids, and new forms of imaging, as well as growing interest in the underlying workings of the brain. One of the most exciting recent insights is the extent to which the brain is plastic, giving birth to new neurons throughout the human lifespan, pointing to great potential for treating and even curing many brain diseases.
These advances are bringing innovative approaches to addressing brain diseases. Optimism also comes from successful new treatments for disorders such as depression, epilepsy, migraine, postnatal depression and spinal muscular atrophy (sma).
It’s time to change your mind
New approaches include neuroimmunology, which targets immune cells in the brain; gene therapy, which offers working genes for those that are broken; and a revived interest in psychedelics, neuromodulation, and precision medicine based on genetic or molecular pathways. Other new approaches such as gene editing, stem cell transplants and rna therapies could also lead to new treatments, as could studies of recreational drugs that attempt to gain insights and therapeutic approaches from their manifestly mind-altering power. Psychiatry is being rethought, with efforts to improve the classification and diagnosis of diseases, and through closer links with neurobiology. Investors, biotech companies and advanced pharmaceutical companies are showing renewed interest in neuroscience. Drug pipes are filling up.
just as well According to the Global Burden of Disease project, 12 mental health disorders affect an estimated 970 million people. Its prevalence has increased by 48% since 1990 as the population has grown. With more than one in ten people affected on the planet, it is a global problem, although the available data point to it being more pronounced in Western countries (see map).
Neurological problems take their own toll. Stroke, dementia, migraine, Parkinson’s, epilepsy and traumatic brain injury are collectively the world’s leading source of disability. Population aging means that the number of deaths from neurological diseases is rising rapidly, especially in low- and middle-income countries.
The brain is often described as the most complex structure in the known universe. It is not surprising, perhaps, that medicine has struggled to remedy its many and varied disorders. However, with new approaches to science and innovative treatments, there is new energy and enthusiasm in the sector. Future discoveries will change brains, minds and lives. ■