Well it’s not actually a journal article
but as everyone and their dog has an opinion on the launch of DSM-5 next week I
thought I would pitch in as well.
First why bother with classification at
all? We have classification because it is useful for communication and
ultimately inevitable. The reason that it is inevitable is that once you
recognize that some people share something in common that other people do not
have – low mood or forgetfulness for example – you are creating a
classificatory system. The other choices are everyone is unique (not that
useful because it means you can’t apply lessons from one person to another) or
that everyone is the same (again not that useful).
So given that we have to have a system of
classification in medicine what should it look like? There are three choices –
classification by symptoms, by course of the disorder or by aetiology.
Until the mid-19th century most disorders
in medicine were classified by symptoms – so a reading of medical textbooks
from the 1700s would have several chapters on different types of fever. This
changed as more knowledge was gained about how the body worked and links were
made between pathology and symptoms in life. For most medical disciplines the
classification changed from symptoms to aetiology so that physicians today
don’t diagnosis central crushing chest pain disorder (a symptom), they
diagnosis a myocardial infarction (an aetiology). Classification by course of a
disorder has been tried in medicine but is never really that successful as it
can only be done retrospectively.
The reason that classification never shifted
from symptoms to aetiologies in psychiatry is that the brain is the most
complex organ in the human body (whose workings we still don’t fully understand),
which is enclosed in a bony box (the skull), making it hard to study (unlike
the heart or pancreas for example). So in psychiatry, with a few exceptions, we
are still stuck with a symptomatic classification of disorders. The trouble
with symptomatic classifications is that they are not really that powerful in
helping decisions about treatment or prognosis – hence the focus on
formulations in training psychiatrists which attempt to take a wider view of
the aetiology and impact of disorders.
Which brings us to DSM-5 This is a classification
by symptoms from a particularly U.S. point of view. The two big criticisms of DSM-5 are that it medicalizes what should be normal and that, while it pretends
to be biomedical, the evidence for the biological basis for most disorders is
lacking.
In my opinion there is considerable merit
in the argument about DSM-5 being an attempt to medicalize the normal – a sort
of “psychiatric mission creep”. The suspicion here is of the influence of
pharmaceutical companies on the designers of DSM-5 to create new markets.
There are many examples of undeclared
conflicts of interest, particularly in U.S. academic psychiatry, influencing
the research agenda and the interpretation of research. The other financial
conflict concerns the American Psychiatric Association who publishes the DSM.
The drafting of DSM-5 has missed most deadlines except the final publication
and launch date, leading to the suspicion that the APA is in poor financial
straits and needs the DSM to come out now in order to collects the money it
makes from its sales.
The second argument about the DSM-5 is that
it does not reflect biological reality and the comparison is often made with
the rest of medicine. However, many disorders in medicine are equally
subjective (pain for example) or their cause is obscure (headaches or migraines
anyone?). Also disorders in other areas of medicine regularly undergo
reclassification (epilepsy or acute coronary events come to mind).
Critics often condemn the “medical model”
when what they really are referring to is a reductionist biological model that
equates all disease with biological pathology. However, anyone who spends any
time on a medical ward round or out-patient clinic will quickly discover that
the “medical model” actually means integrating biology, psychology and
sociology in a complete package.
So in psychiatry we are still left with a
predominantly symptomatic classification to understand people who present with
distress. Our focus should be on improving and defending services for such
people and, as good clinicians, integrating psychology and biology to do
something helpful.
The role of classificatory symptoms is
often exaggerated – the best quote I have heard about them is that “they are
like lines of longitude and latitude – nothing like them exists in the real
world – but they are helpful in finding your way around”.