What is the proper dress attire for a psychiatrist when counseling
patients in his office?

I've seen lots of psychiatrists over the years; some wore business
suits, some wore white lab coats, some wore blue jeans and flannel
shirts. I don't think there is any established dress code.

I have found the same thing as Pink.  I think it depends on the
location and type of office.  You'll find east-coast and mid-west
dresses more conservatively than west-coast.  But it also depends on
the type of office.  More conservative, up-scale offices tend to dress
more conservatively.  Offices that are more laid back, work with kids,
or even just happen to have a casual Friday office policy will tend to
be more casual.  Also more medically oriented settings (i.e.,
hosptials and medical clinics) will tend to dress more conservatively
than more mental health/counseling oriented clinics.  That said,
overall, I'd say the typical attire is buisness casual.

Attire?  Let's focus on whether they are competent and are providing
you with results.