Unlike a generation ago, it is now widely accepted that depression is the
result of brain chemistry gone bad and not some
charactar flaw or weakness. After a stroke, nerve
damage prevents the way certain brain chemicals get
transmitted throughout the brain.
In a brain without
any damage, these chemicals (called neurotransmitters)
are released from the ending of one nerve and then
they hang out in the space between the ending of one
nerve and the top of the next nerve down the line (that
space is called a synaptic cleft and the reason for
the neurotransmitters to stay there for a while is to
give the brain enough time to work out how much of
each chemical it needs to produce).
The neurotransmitters travel throughout the
nervous system being released by one nerve and then
captured by the next nerve down the line and so on,
like a domino effect.
With brain damage those chemicals
go back up into the same nerve they were released from.
The way most
anti-depressants work is by preventing the nerve that
released the neurotransmitter from reabsorbing it and
taking it out of circulation from the rest of the
nervous system.