Other Possible Mechanisms
Table 2 summarizes possible pathophysiological
mechanisms of depression other than those based
on the monoamine-deficiency hypothesis or the
roles of stress, cortisol, and neurogenesis. Many
of these other proposed mechanisms have also
been implicated in psychiatric and neurologic disorders
other than depression. Since the components
of the brain are highly interconnected, it is
not difficult to find possible integrative frameworks
between two or more of the various theories.
Testing the theories in a manner that can reject the null hypothesis has been more difficult.
Research in depression has sometimes been sequentially
imitative of dominant ideas in related
fields, such as neurogenesis, glutamate neurotransmission,
and nicotinic receptors, instead of progressing
on its own path.