Discussion
We have
described a new dimensional rating scheme
that can be used as an adjunct to
conventional categorical diagnosis in order
to provide a richer description of some of
the basic features of an individual's
lifetime experience of psychopathology
relevant to the
bipolar spectrum. The
scheme uses the same data sources as
conventional best-estimate lifetime
diagnosis and is straightforward to use at
the same time as the conventional procedure.
It
retains
several
key
pieces
of
information
that are
lost in
the
simple
diagnostic
process.
In
particular
it
avoids
hierarchical
loss of
information;
it
retains
a
measure
of
severity;
it
accommodates
sub-clinical
cases.
We have
demonstrated
that it
is
straightforward
to learn
and
incorporate
within
the
usual
lifetime
diagnostic
procedures
for use
by a
range of
researchers
including
those
from
psychiatry
and
psychology
backgrounds.
We have
demonstrated
excellent
levels
of
inter-rater
agreement
even
with
diagnostically
challenging
sets of
cases.
Further,
we have
shown
that the
key
information
required
for
correct
diagnostic
decisions
according
to DSMIV
and
ICD10 is
retained
within
the
dimensional
ratings.
Our
group
and our
collaborators
have
extensive
experience
of use
of BADDS
(the Bipolar
Affective
Disorders
Dimension)
as an
adjunct
to
conventional
operational
diagnosis
and it
has been
part of
our
standard
assessment
approach
for over
5 years.
We have
found
that it
is
straightforward
to use
and adds
little
to the
time
taken to
complete
the
consensus
diagnostic
process.
For
researchers,
such as
ourselves,
wishing
to
establish
a
measure
of "caseness"
BADDS
can
easily
be used
to
define
thresholds
– for
example,
a study
of mania
might
require
that
cases be
included
only for
M > 64.
This
would
allow
inclusion
of all
cases
with the
equivalent
of 3 of
more
episodes
of
mania,
irrespective
of
diagnosis.
In a
study of
psychotic
Bipolar
spectrum
illness
it might
be
important
to
distinguish
between
cases in
which
psychotic
features
were a
prominent,
recurrent
feature
of
illness
(rather
than an
occasional
relatively
minor
feature).
Such
individuals
could be
selected
using BADDS as
having P
> 50,
together
with M >
60.
BADDS
can also
easily
be used
in
conjunction
with
categorical
diagnoses
for case
selection.
BADDS
(the Bipolar
Affective
Disorders
Dimension)
was
developed
within
the
context
of
family
studies
and it
lends
itself
to
providing
a
substantially
more
useful
description
of the
milder
("sub-clinical")
end of
the
Bipolar
spectrum
which is
frequently
encountered
within
members
of
families
of probands
with
full-blown
Bipolar
illness.
Conventional
categorical
approaches
often
lead to
unsatisfactory
diagnoses
such as
"Never
ill",
"Major
Depressive
Disorder"
or some
form of
mild
"Not
Otherwise
Specified"
category
when it
is clear
that
there is
some
definite,
albeit
mild,
degree
of
bipolarity.
Within
the
context
of
family
studies
it is
extremely
wasteful
to
discard
such
quantitative
information
about
the
presence
and
extent
of
bipolar
features
and BADDS
provides
a simple
approach
to
making
simple
but
efficient
use of
such
data.
Directly
related
to this
issue,
there is
currently
great
interest
in
delineating
the
breadth
and
frequency
of
expression
of the
bipolar
illness
spectrum
in the
population.
Recent
research,
championed
by Akiskal
and
Angst,
provides
evidence
that
many
cases
that
have
been
regarded
as being
"unipolar
major
depression"
actually
have
subtle
(or not
so
subtle)
bipolar
features
[5,6]
and
classifications
have
been
suggested
that
recognize
several
categories
of
milder
bipolarity
in
addition
to the
conventional DSMIV
categories
of
Bipolar
I and
Bipolar II
Disorders
[eg. [5]].
BADDS
provides
the
capability
to
capture
information
about
this
milder
degree
of
bipolarity
– a
substantial
part of
the M
dimensions
(the
range 0
– 39) is
available
for
rating
sub-clinical hypomanic
features.
The
dimensional
approach
is
particularly
beneficial
for
cases
close to
diagnostic
boundaries.
As any
researcher
or
clinician
knows
who has
undertaken
formal
diagnostic
assignment
using
operational
classifications
such
cases
may be
associated
with a
substantial
investment
of time
in order
to make
a finely
balanced
decision
between
two (or
occasionally
more)
discrete
diagnostic
groups.
It is
common
that
different
raters
come
down on
different
sides of
the
finely
balanced
decision
process
leading
to a
split of
diagnoses
with
eventual
agreement
on a
consensus
but
often
with
further
agreement
that it
is a
"difficult
case"
and that
the
single
category
chosen
does not
quite do
justice
to the
complexity
of the
case. In
contrast,
the
dimensional
approach
of BADDS
(the Bipolar
Affective
Disorders
Dimension)
provides
a scheme
which
can
reflect
that
different
ratings
of such
cases
are
relatively
close on
the
quantitative
scale.
An
example
is
provided
by a
case
considered
in the
formal
reliability
exercise
in which
the
subject
experienced
several
severe
(but not
incapacitating)
major
depressive
episodes
and also
mild
recurrent
sub-hypomanic
episodes.
Of the 7
raters,
4 made a
diagnosis
of DSMIV
Bipolar
Disorder,
Not
Otherwise
Specified
(the
consensus)
and 3 a
diagnosis
of
Recurrent
major
Depressive
Disorder.
In
contrast
the
dimensional
ratings
were
very
similar
across
all
raters
(means
for
those
raters
making
diagnosis
of
Bipolar
Disorder
Not
Otherwise
Specified:
M 27.3;
D 70.3;
P 0; I
blank;
means
for
those
raters
making
diagnosis
of
Recurrent
Major
Depression:
M 23; D
74.7; P
0; I
blank).
The
primary
purpose
in
developing
BADDS
(the Bipolar
Affective
Disorders
Dimension)
was to
use it
as an
adjunct
to
better
describe
some key
features
of cases
and
provide
a simple
mechanism
for case
selection
on the
basis of
these
features. BADDS
has
already
been
used
within
family-based
studies
to
investigate
intra-familial
resemblance
for
lifetime
experience
of mania
and
psychosis
[11]
as well
as
investigating
the
relationship
between
smoking
and
psychosis
in
Bipolar
Disorder
[12].
We are
currently
using
BADDS to
explore
genotype-phenotype
correlations
within
the
context
of both
classical
and
molecular
genetic
studies
of large
samples
of
patients
with
functional
psychosis
and mood
disorder.
There
are
several
limitations
in use
of BADDS,
most of
which
are
common
to other
lifetime
diagnostic
procedures.
First,
and most
obvious,
is that
the
ratings
are
entirely
dependent
upon the
quality
of the
data.
Poor
data
will
inevitably
lead to
poor
dimensional
ratings
as well
as poor
categorical
diagnoses.
It is
essential
that
multiple
data
sources
are used
whenever
possible
that
provide
adequate
description
of an
individual's
lifetime
experience
of
psychopathology
(not
just one
or two
representative
episodes).
As for
any type
of
rating,
poor
data
would be
expected
to
affect
both the
validity
and
reliability
of
ratings.
Second,
ratings
can only
reflect
what is
known of
the
lifetime
experience
of
psychopathology
up to
the time
the
ratings
are
made. In
the
light of
new
episodes
of
illness
scores
on the M
and D
dimensions
may
increase;
those on
the P
and I
dimensions
may
increase
or
decrease.
Third,
subjective
judgments
are
required
in
integrating
multiple
data
sources
and
matching
data to
the
criteria
within
the
guidelines.
Within
the
context
of our
current
approaches
to
psychiatric
classification
this is
inevitable.
Judgements
must
still be
made
about
the
range
for a
rating –
this can
be
equivalent
to
making a
categorical
judgement,
except
that the
different
categories
lie
contiguous
with one
another
on an
ordered
dimension.
Fourth,
there
are
features
of
Bipolar
spectrum
illness
that BADDS
was not
designed
to
capture
–
examples
include
the
presence
and
extent
of rapid
cycling
and the
extent
of mixed
episodes
(although
if all
manic
episodes
are
mixed
this is
denoted
in BADDS
by
adding
an "m"
qualifier
to the M
dimension
– see
rating
guidelines
in
Appendix
A). It
is
possible
for
additional
dimensions
to be
added to
capture
additional
features.
Fifth,
BADDS
was not
developed
for use
in the
general
population.
It was
designed
for use
in
clinical
populations
likely
to
contain
patients
with
Bipolar
spectrum
diagnoses.
The
dimensions
have
meaning
in
providing
an
ordered
measure
of
specific
domains
of
psychopathology.
The
distributions
remain
to be
tested
in
non-clinical
populations
but will
certainly
not
conform
to
normal
distribution.
Sixth,
for the
M and D
dimensions
there is
a
ceiling
effect
in that
these
dimensions
do not
allow
discrimination
between
individuals
having
more
than 11
episodes
of
incapacitating
mania,
or
depression,
respectively.
In
practice,
however,
for the
populations
of
patients
that we
have
studied
relatively
few
patients
score M
= 100 or
D = 100.
Seventh, BADDS is
relatively
poor at
characterizing
cases
where
the
