- Regarding depression as "just" a chemical imbalance wildly misconstrues the disorder. "It is not possible to explain either the disease or its treatment based solely on levels of neurotransmitters," says Yale University neurobiologist Ronald Duman.
- The newest evidence indicates that recurrent depression is in fact a neurodegenerative disorder, disrupting the structure and function of brain cells, destroying nerve cell connections, even killing certain brain cells, and precipitating cognitive decline. At the very least, depression sets up neural roadblocks to the processing of information and keeps us from responding to life's challenges.
- Human emotions take shape in a neural circuit involving several key brain structures, including the hippocampus, the amygdala, and the prefrontal cortex. In depression, faulty circuitry fails both in generating positive feelings and inhibiting disruptive negative ones.
- Stress-related events may kick off 50 percent of all depression and early life stress can prime people for later depression. Ongoing research in animals and in people demonstrates that early strain can alter nerve circuits that control emotion, exaggerating later responses to stress and creating the neurochemical and behavioral changes of depression. In other words, the deeper researchers probe the brain, the more they validate the psychoanalytic view that early adverse life events can create adult psychopathology.
- Depression is not just a disorder from the neck up but a disorder involving many body systems. It both leads to heart disease in otherwise healthy adults and magnifies the deadliness of existing cardiac problems. What's more, it accelerates changes in bone mass that lead to osteoporosis. "The lifetime risk of fracture related to depression is substantial," researchers have declared in the New England Journal of Medicine.
- Just as nerve cell connections can be destroyed in depression, perhaps they can be rebuilt. The common denominator in effective antidepressant treatments, including electroshock, may be their ability to stimulate the sprouting of neurons in key brain regions, literally the forging of behavioral flexibility. An identified neurochemical pathway promises to revolutionize therapy by suggesting ways to do this better and faster.
- The adult brain has a degree of plasticity that is astonishing researchers. "The big news is the structural plasticity of the adult brain, the remodeling of neurons," says neurobiologist Bruce McEwen, Ph.D., of Rockefeller University. "The idea that there are long-lasting, even permanent, changes in structure and function that can affect the way brains process information is the most important part of what we're doing in the lab. We thought that after birth, the brain is a stable organ like a computer that just works away, and no more new nerve cells are produced. The emphasis was on chemical imbalances, as if the circuitry itself was fairly stable. All these changes—cell loss, atrophy of connections—that's very new, and still catching people by surprise."
Uniting Mind and Brain
To understand depression we have to confront the mind/body dilemma head on. Although we often arbitrarily divide the mind from the brain and regard "mental illness" as strictly mental, mood disorders are not disembodied ailments. If depression proves anything, the mind and the brain are one. There are nerve circuits in the brain that color psychological events positively and negatively, that lead us to see rewards and pleasures or merely emptiness and hopelessness, and then to negotiate the world by engaging it or withdrawing from it.
