Abstract
Neurobiological models of obsessive-compulsive disorder (OCD) posit that its clinical symptoms such as repetitive thoughts and behaviors are related to hyperactivity in the cortico–striato–thalamo–cortical (CSTC) circuit. Small scale neuroimaging studies have shown that treatment of OCD is associated with reduced activity across different brain structures within this circuitry. We performed the first meta-analysis of positron emission tomography (PET) and single photon emission computed tomography (SPECT) studies that investigated cerebral blood flow or glucose metabolism in patients with OCD before and after pharmacological or psychological treatment. We calculated standardized mean differences for the regions-of-interest most often reported. The meta-analysis revealed small reductions in activity in the caudate nucleus and orbitofrontal cortex after treatment with a serotonin reuptake inhibitor or cognitive behavioral therapy. Small reductions were also observed in the thalamus when one SPECT study with a large opposite effect was excluded from the analysis. Meta-regression analyses for the caudate nucleus showed no significant effect of the type of treatment, decrease in symptom severity, mean duration until the follow-up scan, or year of publication. These results show that pharmacological and psychological treatments reduce resting CSTC circuit activity, and provide further support for the CSTC circuit model in OCD.
Highlights
Obsessive-compulsive disorder (OCD) is a severe psychiatric disorder that occurs in 2–3% of the general population[1]
FDG-positron emission tomography (PET) studies showed a significant decrease of glucose metabolism in the caudate nucleus (g = −0.18; 95% CI = −0.32, −0.05, k = 8, Z = −2.65, p < 0.01, Q = 7.64, df = 7, p = 0.57, I2 = 0.0), the OFC (g = −0.29; 95% CI = −0.54, −0.03, k = 7, Z = −2.23, p = 0.03, Q = 21.87, df = 6, p < 0.01, I2 = 63.4) and the thalamus (g = −0.30; 95% CI = −0.53, −0.07, k = 5, Z = −2.61, p < 0.01, Q = 7.13, df = 4, p = 0.21, I2 = 29.8)
The analysis that combined PET and single photon emission computed tomography (SPECT) imaging studies showed that successful treatment reduced activity in the caudate nucleus and the OFC
Summary
Obsessive-compulsive disorder (OCD) is a severe psychiatric disorder that occurs in 2–3% of the general population[1]. The most common finding in FDG-PET studies in patients with OCD is decreased LCMRglc in the caudate nucleus after treatment[5,6,7,8,9]. Technetium-99m hexamethylpropylene-amine-oxime (HMPAO) and xenon (Xe-) SPECT techniques measure the cerebral regional cerebral blood flow (rCBF) Studies using these techniques report changes in the rCBF after treatment in the caudate nucleus, putamen, thalamus, orbitofrontal cortex and prefrontal cortex[14,15,16,17,18,19]. The results of those studies are typically based on small sample sizes, limiting the generalizability of the findings from the individual studies To overcome these limitations, we performed the first meta-analysis of studies that have assessed resting cerebral blood flow or glucose metabolism in patients with OCD before and after pharmacological or psychological treatment. To explore whether variability in the study methods (e.g., type of therapy) and patient characteristics (e.g., level of symptom improvement) could explain variability in the results, we performed additional meta-regressions
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