The new somatic symptom disorder in DSM-5 risks mislabeling many people as mentally ill

I concur with Professor Frances’ view that the new somatic symptom disorder(SSD)in DSM-5 is vague and risks labelling many people as mentally ill.

There is an evolving understanding of the aetiology of mental disorders over the last decade. Recent advances such as the findings of anti NMDA antibodies in anti NMDA encephalitis (NR1) and NPSLE (NR2A and NR2B), anti thyroid antibodies (Hashimoto’s encephalopathy) and mitochondrial diseases as causes of psychiatric syndromes, take us beyond the traditional paradigm of neurotransmitter dysregulation. One particular characteristic of these disorders is that the presentations span multiple specialties (rheumatolgical, neurological, haematological, psychiatric, gynaecological, endocrine) and have neuropsychiatric involvement as the primary manifestation. These disorders can present with isolated somatic symptoms (e.g. headache, fatigue, neuropathy, loss of movement, movement disorders etc) that fluctuate in presentation requiring the assessing clinician to have a high index of suspicion combined with a thorough exploratory approach to identify the core aetiology.

In clinical practice, the referral pathways to psychiatry make an implicit assumption that organic possibilities have been ruled out by the referring GP or physician. This may lead to medical illnesses being missed unless a through biochemical and medical evaluation is carried out.1 The blood-brain barrier is no longer impenetrable as it was once considered to be, making the mind-body dichotomy an obsolete paradigm. The interface between general medical illnesses and psychiatric disorders is susceptible to two particular biases namely referral bias and spectrum bias which often leads to issues of contention in management.

Patients are referred to the respective specialty based on the presenting distressing complaint. The aetiology of the presenting complaint may, however, not be within the common differential diagnoses of the assessing clinician which leads to a referral bias. For example, a patient complaining of memory dysfunction seeing a psychiatrist may have antiphospholipid syndrome as the primary cause of memory dysfunction which requires a rheumatological/haematological input. Similarly, 75 % of Anti NMDA encephalitis present initially to psychiatrists and are misdiagnosed with a psychiatric disorder.2 It is due to neurological signs or deterioration that a neurological input is sought. Milder cases or incomplete cases (formes frustes) however, may continue to be treated as psychiatric illnesses.2 Thus, the lack of an aetiological approach in psychiatry can miss a modifiable cause.

The other issue in the mind-body interface is a spectrum bias. Evidence suggests that psychiatric disorders can be conceptualised as manifestations of a multisystem disorder.3 Serological investigations may not always detect early manifestations of systemic diseases in psychiatric patients. Thyroid dysfunction and autoimmune diseases such as Systemic Lupus Erythematosus (SLE) are two such examples. The brain has the highest concentration of thyroid receptors than any other organ and is extremely sensitive to changes in the thyroid hormone.4 Furthermore the brain concentrations of T3 and T4 are different from levels found in the periphery.5 Thus, the reliance on the TSH for the diagnosis of thyroid dysfunction in psychiatry may be misleading. TSH has been validated in an endocrine population that may represent a late spectrum of disease and hence may have a poor negative and positive predictive value in a psychiatric population. The ‘great mimic’ SLE presents with multisystem involvement that occurs at any point in the person’s life, requiring the assessing clinician to take a longitudinal perspective in assessment. The criteria for SLE however, represent a late spectrum of disease and do not take into account evidence that the brain may be affected early in the course of the disease even before the other criteria for SLE are met.6,7

According to Mayberg, as our understanding of brain mechanisms mediating complex behaviours continues to grow, the arbitrary operational boundaries separating the clinical disciplines of psychiatry, neurology and immunology become increasingly blurred, requiring new holistic approaches in the study of neuropsychiatric disorders.8 Oyebode and Humphreys recently proposed a paradigm shift in psychiatric training to include training in other specialties like immunology, endocrinology and cardiology.9 The current categorical approach in psychiatry, the validity of which has been questioned, can exclude active consideration and treatment of medical conditions which may be etiologically related. The brain being sensitive to neurotransmitter, neurochemical, neurohormonal and vascular changes may be affected even before the systemic effects on the rest of the body are evident.

Based on my clinical experience, I would propose the adoption of a Multisystem Medical Evaluation (MSME) with the aim of identifying etiological mechanisms in psychiatric evaluation before a diagnosis of SSD is made. Furthermore, a case conference incorporating various specialties should be a prerequisite before this diagnosis is made. The MSME consists of a pan-system history taking and clinical examination based on our existing knowledge of medical aetiology of psychiatric disorders10 to guide investigations and further exploration based on clinical suspicion. This would span a brief immunological, endocrine, vascular, nutritional, structural (trauma, epilepsy) disorder evaluation in addition to the predominant psychiatric evaluation. History taking should guide the clinician to place appropriate weight in the different domains. A brief tailored MSME is useful in routine psychiatric practice as it incorporates a true bio-psycho-social approach. It recognises the important role psychiatrists can play in the detection of physical illness at an early stage.

In summary, the SSD diagnosis is likely to cause more harm than good, shifting the balance towards a diagnosis that would lead to mismanagement of patients. It is a step back in time, is not in line with current advances in psychiatry and reminiscent of diagnoses like hysteria. It would be prudent to heed Plato’s age old advice ““The greatest mistake in the treatment of diseases is that there are physicians for the body and physicians for the soul, although the two cannot be separated."

References:
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2.Kayser MS, Kohler CG, Dalmau J. Psychiatric manifestations of paraneoplastic disorders. American Journal of Psychiatry 2010;167(9):1039-1050.
3.Leboyer M, Soreca I, Scott J, et al. Can bipolar disorder be viewed as a multi-system inflammatory disease? Journal of Affective Disorders 2012; 141: 1-10.
4.Shahrara S, Drvota V, Sylven C. Organ specific expression of thyroid hormone receptor mRNA and protein in different human tissues. Biol Pharm Bull 1999;22:1027–33.
5.Bauer M, Heinz A, Whybrow PC. Thyroid hormones, serotonin and mood: of synergy and significance in the adult brain. Molecular psychiatry 2002;7(2):140.
6.Wallace DJ, Hahn BH. Dubois' Lupus Erythematosus, 7ed. Lippincott Williams & Wilkins. 2007
7.Petri M, Naqibuddin M, Carson KA, et al. Brain magnetic resonance imaging in newly diagnosed systemic lupus erythematosus. Journal of Rheumatology 2008;35:2348-2354.
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10.David, A. Lishman's organic psychiatry: a textbook of neuropsychiatry. Wiley-blackwell. 2009