Definition and Overview
Somatic symptom disorder (SSD) is defined in DSM-5 (2013), it is a diagnostic category reorganized by integrating parts of the existing somatization disorder, undifferentiated somatoform disorder, pain disorder, and hypochondria. Unlike DSM-IV's requirement for 'medically unexplained' symptoms, DSM-5's SSD can be diagnosed when the psychological response to symptoms is excessive even if there is a medical cause.
It occurs in approximately 5-7% of the general population, and in primary care settings, SSD affects approximately 5-10% of patients. It is about twice more common in women than in men, and occurs after middle age. Healthcare utilization is high, healthcare expenditures are increasing, and functional disability and decline in quality of life are evident.
Diagnostic criteria
The DSM-5 diagnostic criteria are as follows:
- One or more physical symptoms that are painful or interfere with daily functioning. B. Excessive thoughts, feelings, or behaviors related to physical symptoms or related health concerns, as evidenced by one or more of the following: (1) Excessive and persistent thoughts about the severity of symptoms; (2) persistently high anxiety about health or symptoms; (3) Excessive time and energy spent on these symptoms or health concerns. C. Even if no single physical symptom persists, the symptomatic condition persists (usually more than 6 months).
Relationship with the autonomic nervous system
Stress and psychological conflict can be converted into physical symptoms through the autonomic nervous system. Activation of the HPA axis causes cortisol to be secreted, and overactivity of the sympathetic nerves causes various physical reactions.
Central sensitization is one of the key neurobiological mechanisms of somatic symptom disorder. Chronic stress and psychological arousal alter the pain-regulating systems of the spinal cord and brain, causing normal physical sensations to be interpreted as pain or discomfort. This is a mechanism shared with fibromyalgia, chronic fatigue syndrome, and irritable bowel syndrome.
Heart rate variability (HRV) studies consistently report that SSD patients have lower HRV than normal controls, and in particular, parasympathetic indicators are reduced. This is associated with a decline in the ability to control emotions, and can be used as a biomarker to predict treatment response.
Association with functional somatic syndrome
Somatic symptom disorder overlaps with a number of functional somatic syndromes. Fibromyalgia, chronic fatigue syndrome, irritable bowel syndrome, persistent postural dizziness (PPPD), non-cardiac chest pain, chronic back pain, and tension-type headaches are all included in or associated with the spectrum of SSD. These diseases share autonomic nervous system dysfunction and central sensitization as common mechanisms.
Functional neurological symptom disorder (formerly known as conversion disorder) is a case in which neurological symptoms such as paralysis, tremors, convulsions, visual or speech disorders, etc. are caused by functional mechanisms, and is classified separately from SSD, but is related.
treatment
In a Cochrane review, cognitive behavioral therapy (CBT) was found to be effective in reducing symptoms of SSD. Gradually increasing physical activity, improving sleep hygiene, and stress management techniques also contribute to improving symptoms.
Mindfulness-based cognitive therapy (MBCT) and acceptance and commitment therapy (ACT) are also used to treat SSD. Psychoeducation, that is, an approach that explains the mechanisms of physical symptoms so that patients can understand them, is important in improving motivation for treatment.
As drug treatment, tricyclic antidepressants (TCAs, especially amitriptyline) and SSRIs/SNRIs are effective in improving pain, fatigue, and mood. Treatment of concurrent depression or anxiety also contributes to improving SSD symptoms.
The quality of the doctor-patient relationship has a strong influence on treatment outcome. It is important to take an approach that acknowledges and empathizes with the symptoms while simultaneously setting goals for functional recovery.