Depression is marked by a profound and constant sense of
hopelessness and despair – symptoms that interfere with
a person's ability to work, study, sleep, eat, and enjoy once
pleasurable activities. It is a complex disorder that can
be attributed to many different factors, including emotional,
environmental and biological influences. It has been shown
to run in families and it tends to recur.
The causes of depression are not understood. Early biological
hypotheses considered that depression was caused by an imbalance
of important chemical messengers in the brain called neurotransmitters.
Current antidepressant therapy alleviates many of the symptoms
of depression, perhaps in part by correcting some of the prior
chemical imbalances. However, just because antidepressants
help some depressed patients does not mean that a chemical
imbalance was the cause of depression, nor does it help those
who do not respond to current antidepressants. And, even if
the imbalance view were partially correct, we do not understand
why it takes 1-2 weeks after treatment starts before notable
recovery is detected.
There is a growing body of evidence which suggests that depression
may actually be a special kind of neurodegenerative disorder.
We know that some people suffering from depression have structural
changes in their brains compared to people who do not suffer
from depression. Imaging studies and postmortem examination
of the brains of depressed patients have consistently found
a loss of neurons in specific brain regions, such as the hippocampus
– a small part of the brain that is vital to the storage
of memories. In fact, the hippocampus is smaller in women
with a history of depression than in those who've never experienced
this illness. Currently, attention is being paid to the concept
that antidepressant medications may help bolster an inadequate
formation of new hippocampal neurons, a concept that was totally
unexpected as few as 5 years ago.