There is nothing mystical about the act of understanding.
 Sometimes it may seem like it, when one has an Aha! moment,
or when understanding emerges in the context of meditation or spiritual
reflection, but there really is nothing supernatural about it.

Understanding, after all, is merely an act of description.  It
arises from the collation of observations.  

To understand something is to be able to describe that thing on all
pertinent levels of abstraction.  In the case of mental
illness, that means description on levels from the molecular to the
sociocultural.  At least at this time.  It may be
that quantum mechanics is involved, in which case you’d have to go
beyond the molecular level to the subatomic level.

Sometimes I hear people talking about getting to the root of the
matter, or the core issues, or something like that, and I feel
perplexed.  The nexus of observations necessary to understand
what is going on is an ill-defined n-dimensional space.  It
does not have a core, or roots, or anything like that.  There
is no surface; thus, there is nothing beneath the surface.

And no part of the knowledge space is more important, a priori,
than any other part.  

That is not to say that it is impossible to rank the knowledge in terms
of degrees of importance.  It is just that what makes one
aspect more important that another changes according to context.

Sometimes, what is important at the moment is 5-HT, or maybe even href="http://scienceblogs.com/purepedantry/2006/08/deletion_mouse_shows_resistanc.php">TREK-1.
 Sometimes it is the tissue level, such as href="http://scienceblogs.com/smoothpebbles/2006/08/neurologist_helen_mayberg_in_s.php">Area
25.  Sometimes you have to forget all that, and look
at href="http://scienceblogs.com/dispatches/2004/12/homeless_veterans.php">society
and culture.  

Sometimes, it is hard to know which is the important part of the
knowledge space to pay attention to.  Sometimes, you just have
to listen to the patient, who usually will tell you what is
important.