I have posted in the past about the similarities between
rheumatology and psychiatry. The
classification systems are the same, there is a lot of diagnostic flexibility,
all of the conditions are very heterogenous, the underlying pathophysiology is
not clear, and the mechanisms of action of most of the treatments used are
unknown. I thought I would do a similar
comparison with Dermatology. As an acute
care psychiatrist I noticed that dermatology problems are frequently ignored by
both patients and physicians or treated incorrectly with over-the-counter
preparations. There is some overlap with
both psychiatric and neurological conditions, but most of the skin conditions I
detected were not in that category. I
was always grateful I had specialists available who could see my patients
quickly. In some cases, the treatment
was lifesaving.
Dermatology is a classic example of pattern-matching in
diagnoses and if you missed it I will post my favorite case here. It happened in medical school on an
infectious disease rotation. We were asked to see a patient for spontaneous
bacterial peritonitis, an infection of ascitic fluid in the abdomen. After reviewing all the preliminaries, we
came into the patient’s room with the attending. From across the room the attending said:
“What am I seeing from here that needs to be addressed?” We all looked puzzled. He came across the room and pointed out a
large confluent pink rash on the man’s left ankle. He aspirated a small sample
from the edge of the rash and sent it to his lab for further analysis. He was an
expert in streptococcal infections and guessed what type of strep it would
be. He picked an antibiotic that he
thought would work for both conditions.
The prevalence and comorbidly of dermatology diseases is
high. At any given moment 25-33% of the
world’s population has one of these diseases (1). That may be as high as one in three Americans
in the US (2). Some studies have
suggested the point prevalence may be much higher (up to 64% in some studies)
because people are unaware of the fact that they have the diseases (like
rosacea and actinic keratoses). Studies also have variable inclusion criteria
for the 5 most common diseases to all possible diseases. Variability also exists within the same
category like atopic dermatitis that can range from 2.6 – 9.6% and in some cases those authors
point to variable diagnostic criteria.
To illustrate some of this variability consider the following case:
66 YO man with a history of asthma and anaphylactic
reactions. No history of atopic
dermatitis as a child but newly diagnosed in his 60s when it presented with
intense pruritic and patchy crusty lesions that were not associated with
scratching. He also had a recent 24 hr. cardiac monitor and had similar
crusting lesions at the electrode sites for two weeks after they were removed.
He has also been seeing a dry eye specialist for a severe dry eye problem that
interferes with his work. The dry eye
specialist has diagnosed Meibomian Gland Dysfunction. He uses artificial tears
6-8 times a day, eyelid scrubs, and occasional ocular glucocorticoids for
relief. On exam he is noted to have
patchy lesions on his shoulders, an erythematous rash on his right medial
thigh, and an erythematous rash with skin peeling on his right palm. Examination of the scalp shows flaky dandruff
with oily inflamed patches. He has areas
of facial induration with some facial acne with redness and indurated
subcutaneous patches not associated with the acne. Some of of those areas of
induration are tender.
The final dermatology diagnoses based on exam and clinical
picture are: atopic dermatitis, contact dermatitis, rosacea,
seborrheic dermatitis of the scalp, and probable ocular rosacea. The
recommended treatment includes a topical facial medication containing azelaic
acid, metronidazole, and ivermectin, topical glucocorticoids for the seborrhea
and atopic dermatitis, prescription strength (5%) ketoconazole shampoo twice a week, and
CeraVe applied to all areas of the body with active rash or pruritic from
atopic dermatitis. None of the medications are curative and are to be used on a
maintenance basis as needed with annual follow up visits. Dry eye follow up is separate per that
specialist. Despite 3 diagnoses, this
patient has 5 distinct lesions for atopic dermatitis, 4 distinct lesions for
rosacea, and 2 for seborrhea.
How does all this aid in understanding the typical social
media criticisms of psychiatry? Here are
a few:
1: Number of
diagnoses: I have looked at this
issue in detail and counted the diagnoses in the DSM-5 several ways. According
to the American
Board of Dermatology, dermatologists are trained to recognize and treat
over 3,000 diagnoses of skin disease. Does it seem reasonable that the most
complex organ in the human body might have at
least 281?
2: High prevalence: typical social media criticisms of psychiatry
focus on the high prevalence of disorders and the treatment of those
disorders. Many wellness industry
influencers use this as a basis for suggest that lifestyle changes and whatever
products they are hawking are the real solution and the problem is excessive medical
care. Some point prevalence studies suggest that dermatology conditions may be
as high as 68% of the population and that there are always millions with the
most common conditions like atopic dermatitis (2-10%), seborrheic dermatitis
(4%), and psoriasis (2-3%). There are
also single syndromes that have very high reported prevalence in the literature like Sensitive Skin Syndrome that is reported to have a prevalence
of 60-70% in women and 50-60% in men.
Self-reported skin sensitivity decreased with age and reported
severity. 11% of men and 19% of women 25
years of age or less reported their skin was sensitive or very sensitive
compared to 7% and 12% respectively at or greater than age 55. (20)
3: Heterogeneity: Social media criticism and some research go to absurd lengths to show that
psychiatric conditions are heterogeneous.
When that is studied in dermatology the heterogeneity is just as
significant. The reality is that biology produces heterogeneous individuals and
diseases and heterogeneous diseases in the same individual.
As an illustration, consider the following simple calculation the flows from polygenes or a disorder determined by multiple genes. A recent study of major depression (23) found 697 associations across 636 loci. Since each locus has the 3 possible states (homozygous dominant - AA, heterozygous - Aa, and homozygous recessive - aa) a first approximation of the total number of gene combinations is 3^636 = 2.812 x 10^303. This is an impossibly large number, but it does indicate the massive amount of information that relatively simple biological configurations can carry. On this blog I have examined attempts to look at the combinations of diagnostic criteria and their real-life shortcomings. The best contrast was a group who suggested that large number of diagnostic feature combinations meant that psychiatric diagnoses were “unscientific” and a group who actually examined the features in clinical practice and determined they were manageable. The latter group showed that there were 225 possible combinations for major depression and about ¼ of them did not appear in a single patient.
The above approximation based on polygenes is problematic at a couple of levels – foremost is that not all polygenes are as likely to be associated with the disorder. That analysis requires more advanced statistical methods (24). But even considering modest number of contributing genes explains heterogeneity, severity differences, and treatment resistance. I will take it a step further and suggest that anyone who does not appreciate that heterogeneity is a feature of biology and not a problem for diagnosis lacks a basic understanding of biology and medicine.
4: Comorbidity:
A 2022 study showed that (after excluding cancer screening) 43.35%
reported having had at least one dermatological condition or disease in the
past 12 months with 35.38% had one skin disease, 24.32% had two skin diseases,
14.06% had three skin diseases, and 26.34% had four skin diseases or more. Critics seem to think that comorbidity is a
weakness of psychiatric diagnosis when every other specialty recognizes
equivalent or greater amounts of comorbidity.
5: Diagnostic
certainty: In the past I taught a
course in diagnostic thinking to medical students. One of my cited references was a paper
comparing the diagnostic expertise of dermatologists to primary care physicians
on a standard set of photos about dermatology diagnoses (13). The evidence on evaluating clear cut cases of
dermatological disease and equivocal cases the dermatologists are much better
than non-specialist physicians. The
diagnostic process in dermatology also suggests that pattern-matching is
probably a more significant factor than rules-based processes for experienced
physicians. By rules based processes – I mean written diagnostic criteria. There
is no reason to think that pattern
matching does not apply in psychiatry at several levels.
Pattern matching also speaks to different phenotypes in the
same individual. In the case example, this man has several different
equivalents of the same underlying disease – 5 variants of atopic dermatitis
and 2 for rosacea all on his body at the same time.
6: Underlying
pathophysiology: The standard social
media caricature of psychiatry is that it is a poorly defined morass of
conditions with no known specific etiologies or pathophysiology. In fact, 67%
of DSM listed diagnoses have either a known pathophysiology or a specific
medical test. Every psychiatric
diagnosis has a medical differential diagnosis.
It is why psychiatrists are medical specialists. The same is true for
dermatological disorders and there are many cutaneous manifestations of
underlying medical conditions. In addition to medical causes of both
psychiatric and dermatological conditions there are two addition important
areas of overlap.
The first are conditions where there is no known clear unitary
pathophysiology. On the dermatology side
there are many common and rare conditions like atopic dermatitis, seborrheic
dermatitis, acne vulgaris, rosacea, psoriasis, granuloma annulare, vitiligo,
lichen planus, erythema multiforme, bullous pemphigoid, and pemphigus vulgaris.
Many have one or more hypotheses about the pathophysiology, and these
hypotheses guide treatment attempts. The case report above is a clear example
of multiple treatments contained in the same topical medication for rosacea.
The major psychiatric disorders when underlying medical causes have been ruled
out are in a similar situation. Over the
past 30 years there have been over 100 hypotheses about the pathophysiology of
depression and recently (21) some of these hypotheses have been combined.
The second are conditions where there is overlap between
psychiatry and dermatology sometimes called psychodermatology. A study by Balieva, et al (19) examined the
bidirectional relationship between skin disorders and psychiatric
disorders. It was a large registry study
from Norway that selected patients based on their seeing dermatologists and
being treated for common disorders with psychiatric disorders being the outcome
variable. That population was compared
to a non-dermatology diagnosis groups and odds rations were calculated. The
authors demonstrated that patients were 2-3 times as likely to develop
depression given the dermatology diagnoses with elevated risks for anxiety,
somatoform disorders, and obsessive-compulsive disorder but not eating disorders.
The authors reconciled this with several previous studies with similar findings,
but they broadened the number of psychiatric diagnoses.
Psychodermatology classifies the combination of psychiatric
and dermatological disorders based on which disease is primary and whether the
skin pathology is a manifestation of psychopathology (delusional parasitosis,
trichotillomania, pathological skin picking, and psychogenic pruritis.). In a recent study (17), the latter group
had a very high risk of neuropsychiatric disorders – depression, anxiety
disorders, and personality disorders.
Dermatology conditions exacerbated by stress including atopic dermatitis,
psoriasis, acne vulgaris, and vulvodynia – were all associated with depressive
disorders, sleep disorders, and neurodevelopmental disorders.
7: Mild-moderate-severe
designations: Another common
criticism of psychiatric diagnoses is that it seems like the following
qualifier in most diagnostic criteria is arbitrary:
The disturbance causes clinically significant distress or
impairment in social, occupational, or other important areas of functioning.
Since there are no formal diagnostic criteria for
dermatology there is no threshold for diagnosis. That is not necessarily problematic since the
many intermediate phenotypes for any major psychiatric disorder may also not
meet this threshold but nonetheless seem like a good idea to treat. In dermatology practice there is a
significant cosmetic component that can be purely subjective. Many studies have mild-moderate-severe
categorizations based on the judgment of clinicians. In dermatology, the disappearance of the
cutaneous manifestations often leads to the patient stopping treatment when the
treatment needs to be continued. An
example is the use of emollients in atopic dermatitis and avoiding skin
irritants.
8: Medications with clearly defined mechanism of action:
Glucocorticoids (prednisone, triamcinolone, betamethasone) have potent effects
on inflammatory and immune responses that are not disease specific. Biologics for dermatology conditions can be
pathway specific for inflammatory pathways, but they are not technically
disease specific.
I reviewed 11 monoclonal antibodies used for dermatology
diseases and found that they are characterized as pathway specific but not
disease specific. In other words, they
shut down specific inflammatory pathways that can be involved in more than one
dermatological disease and there is overlap with other allergic, rheumatic, and
inflammatory diseases as well as cancer.
On larger scale, the overlap between immune medicated conditions obviously cuts across the turf of multiple specialties. That includes several CNS diseases that produce neuropsychiatric syndromes and may soon include purely psychiatric disorders with no other identifiable causes (22).
9: Transdiagnostic considerations: there has been and explosion of the use of
the term “transdiagnostic” in psychiatry – typically as a criticism to suggest
that diagnostic categories are cruder than in the rest of medicine. The term is
just being extended to other commentaries.
In the case of dermatology – rash is considered one of the leading
symptoms that leads to medical evaluations. Here is a list of 71 causes of a rash. But the transdiagnostic concept does not stop
there it also applies to treatments across several categories that are
non-specific but effective.
Transdiagnostic was initially considered based on the
assumptions that disorders had similar etiological and maintenance factors and
responded to non-specific therapies like cognitive behavioral therapy (16). One of the associated criticisms was that
categorical diagnosis was less specific due to high comorbidity. In a systematic review of 116 studies only 3%
met standardized criteria (Mansell) for a study of transdiagnostic approaches
in psychiatry (16). That same study reviewed all the commonly used approaches. The authors conclude that transdiagnostic
approaches have overpromised and undelivered.
The authors present an extensive discussion of the problems some of
which are evident in a typical network diagram they include in their paper. I want to focus on just one – and that is: “transdiagnostic
approaches are largely based on an epistemological error, which triggers an
illusion of continuity”. When
classification systems like the DSM and ICD use simplified language – psychopathology is ignored and it collapses
reality into unitary disorders. Suddenly
all depression is equivalent to a handful of criteria. A depression checklist like the PHQ-9
suddenly becomes a phenotype for large epidemiological studies and a basis for transdiagnostic
treatments.
What happened to the endophenotypes of the recent past? If there is any variance in clinical practice
it all seems to be swept into a spectrum or a continuum like electromagnetic radiation.
The real patterns that physicians have diagnosed and treated with success over
the years are collapsed into a number on rating scale and there are as many
rating scales as you want.
The dermatology diagnoses discussed so far are clear reasons
why we need to keep the patterns real. Recognizing the importance of those
patterns is why there is no PHQ-9 for atopic dermatitis. This process has often been oversimplified as
prototypical diagnoses in the past – but there are no protypes when you
are recognizing hundreds of different microphenotypes rather than one large
oversimplified one.
10: Polypharmacy,
cure, and discontinuation:
Deprescribing has become the latest buzzword used to criticize
psychiatry as if psychiatrists have never discontinued medications in the past
and do not know how to do it. As far as
I know this has not be a problem focused on dermatology, but many papers say
that patients frequently stop their medications prematurely because they are
worried about using them on a long-term basis.
With all complex polygenic illnesses – being followed by a physician
familiar with your problem who can monitor the course of the illness and make
the appropriate adjustments is the best course.
That is necessary because most of these diseases are genetically complex
and not predictable. Detrimental genotypes may never be expressed or in the
case presented occur in old age rather than youth. Environmental factors are also
important. Physicians are all generally
trained to do that monitoring and decide when the medications can be stopped or
held. In the case where a maintenance medication
is needed, they also have a goal of minimizing side effects from it.
I am hoping that the above comparisons make sense. Much of
the hyperbole focused on psychiatry is not based in how psychiatry is taught or
practiced. Psychiatry is often isolated
from the rest of medicine when it uses the same diagnostic and treatment
approach. It has the same genetic architecture as other polygenic diseases. Even though the DSM has
criteria listed for diagnoses – a diagnosis by a psychiatrist is much more than
that. Just like a dermatologist can see
several diagnostic equivalents rashes, a psychiatrist is able to recognize many
phenotypes of illness that are equivalent to the classification. Those phenotypes include both validity
markers and psychosocial characteristics that are not listed in the DSM but are
important for individualized care. And
contrary to what you might read – it does not take an extensive battery of
testing to get results.
George Dawson, MD, DFAPA
Supplementary 1:
In human embryology the skin and the brain both originate form the same germ layer - the ectoderm. The ectoderm differentiates into the neuroectoderm and surface ectoderm that eventually becomes the epidermis and the surface appendages (hair and nails)
Supplementary 2:
A typical polygenic risk analysis is available at the top of this post: https://real-psychiatry.blogspot.com/2024/04/what-economist-doesnt-know-about.html
Note that this patient is at risk for 9 dermatology and 9 psychiatric conditions according to this graph.
Graphics Credit:
Lead graphic is from:
Boguniewicz, M, Fonacier L, Leung DYM. Atopic and contact dermatitis. In: Rich, Robert R., Fleisher, Thomas A, Shearer, William T., Schroeder, Harry, Frew, Anthony J., Weyand, Cornelia M. Clinical Immunology : Principles and Practice, 5th ed. London: Elsevier; 2018 : p. 614
License number: 1693945-1
Graphics 2 and 3 were generated by me from FDA package inserts in Graphic 2 and the Table of Contents of the leadg graphics text (Rich R, Shearer TA, et al) and several research papers in the case of Graphic 3.
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