(PS7-7) Central Nervous System Sensitization: Potential Shared Mechanisms in Obsessive-compulsive Disorder and Chronic Pain

The burden of OCD includes vulnerability to comorbid conditions. However, one comorbidity, chronic pain, has been vastly overlooked. Chronic pain is defined as pain lasting three months or longer, and common chronic pain conditions include fibromyalgia, temporomandibular joint disorder (TMD), chronic migraine/tension headaches, irritable bowel syndrome IBS), chronic fatigue syndrome, and chronic low back pain. OCD and chronic pain may share underlying mechanisms that leave individuals with OCD especially vulnerable to developing co-morbid chronic pain. Central nervous system sensitization (“central sensitization”) is an amplified or increased responsivity to somatosensory and emotional input that occurs via upregulation of circuits in the central nervous system (CNS). As a result, a real, genuine pain experience can be produced by the CNS in the absence of noxious stimuli. Central sensitization plays a key role in the development of chronic pain and may also play a mechanistic role in the co-occurrence of OCD and chronic pain. Moreover, before the discovery of central sensitization processes revolutionized pain science in the last decade, many of these chronic pain experiences in the absence of tissue pathology were dismissed as “psychosomatic” and went untreated. This may have resulted in an under recognition of shared mechanisms of OCD and chronic pain due to pain experiences being dismissed as “OCD” or “anxiety.” Chronic pain is associated with demoralization, suicide risk, and previous work has shown that outcomes for mental health treatment are reduced in the presence of unaddressed chronic pain. Taken together, addressing critical gaps in our understanding of co-occurring OCD and chronic pain is crucial because: 1) identifying shared mechanisms between OCD and chronic pain would support the future use of treatments targeting both disabling conditions; and 2) chronic pain might contribute to increased clinical complexity in OCD and may be associated with important clinical outcomes including quality of life and impairment.
Preliminary data (N = 131) was collected by the first author in a residential/partial hospitalization program for OCD. The sample on average was 29.5 years (SD = 10.0), 46% women (49% men, 5% other), 86% white, and average OCD severity was 25.7 (SD= 5.1). Using the DSM-5 Cross-Cutting Symptom Measure, 35% of patients endorsed being bothered by at least mild, unexplained pain several days per week. Approximately 21% of the sample endorsed moderate to severe levels of unexplained pain. This indicates a significant proportion (e.g. 35%) of OCD patients attempting to engage in intensive OCD treatment are concurrently struggling with physical pain. A sub-sample of these patients (N = 37) completed the Central Sensitization Inventory (CSI), which assesses symptoms of CNS sensitization resulting in hypersensitivity to both noxious and non-noxious stimuli. This measure was highly related to self-reported pain (Spearman’s r = .67). Additionally, the CSI was moderately related to functional impairment (Pearson’s r = .23), and negatively related to quality of life (e.g. central sensitization is associated with poorer quality of life, Pearson’s r = - .42). Implications for future research will be discussed.