Common Pathways for Pain and Depression-Implications for Practice

Substance P's Impact on Chronic Pain and Psychiatric Conditions-A Narrative Review

Substance P (SP) plays a crucial role in pain modulation, with significant implications for major depressive disorder (MDD), anxiety disorders, and post-traumatic stress disorder (PTSD). Elevated SP levels are linked to heightened pain sensitivity and various psychiatric conditions, spurring interest in potential therapeutic interventions. In chronic pain, commonly associated with MDD and anxiety disorders, SP emerges as a key mediator in pain and emotional regulation. This review examines SP's impact on pain perception and its contributions to MDD, anxiety disorders, and PTSD. The association of SP with increased pain sensitivity and chronic pain conditions underscores its importance in pain modulation. Additionally, SP influences the pathophysiology of MDD, anxiety disorders, and PTSD, highlighting its potential as a therapeutic target. Understanding SP's diverse effects provides valuable insights into the mechanisms underlying these psychiatric disorders and their treatment. Further research is essential to explore SP modulation in psychiatric disorders and develop more effective treatment strategies.

Impact of painful physical symptoms on first-episode major depressive disorder in adults with subthreshold depressive symptoms: A prospective cohort study

OBJECTIVE

To investigate the impact of baseline painful physical symptoms (PPS) on subsequent first-episode major depressive disorder (MDD) in adults with subthreshold depressive symptoms, including subgroup analyses to assess whether the associations differ in individuals with and without physical diseases.

METHODS

A total of 2343 adults with subthreshold depressive symptoms were recruited at 34 primary health care centers. PPS were measured at baseline. First-episode MDD during follow-up was diagnosed by professional psychiatrists using the Mini-International Neuropsychiatric Interview.

RESULTS

Baseline PPS showed independent impacts on first-episode MDD in adults with subthreshold depressive symptoms without physical diseases, but not in those with physical diseases. A non-linear association (P < 0.001) was observed between PPS burden and the risk of first-episode MDD. The HRs for first-episode MDD exhibited a rapidly increasing trend between PPS burden scores of 10-16, and maintained consistently high when scores exceeded 16. The analyses for specific PPS revealed that headache, neck pain, and heart or chest pain were independently associated with first-episode MDD in participants without physical diseases, the HRs were 1.57 (1.15-2.36), 1.53 (1.02-2.30), and 1.69 (1.14-2.50), respectively. Further network analysis demonstrated that heart or chest pain serves as a bridge symptom among the seven specific PPS and first-episode MDD in those without physical diseases.

CONCLUSION

PPS burden and heart or chest pain may be significant indicators for first-episode MDD in adults with subthreshold depressive symptoms without physical diseases. Future studies should investigate whether interventions targeting PPS can prevent episode MDD in this subthreshold population.

Chronic pain predicts a worse response to depression treatment, regardless of thyroid function or psychotropics prescribed

BACKGROUND

Chronic pain (CP) and thyroid hormones' (TH) abnormalities are associated with depression, but the impact of pain and TH fluctuation on the response to depression treatment is uncertain.

METHODS

Eighty-eight patients with major depression were evaluated before and after 6 months of specific treatment, through scales of symptoms' severity (HAM-D-17), psychomotor disturbance (CORE), and quality of life (WHOQOL-Bref). We reviewed psychiatric medications and measured TSH, T3 and T4. We used Generalized Estimating Equations to assess the interaction effect between CP and treatment time on depression severity and TH levels, and Bonferroni to compare means.

RESULTS

47.7 % of the patients had CP. Patients with and without CP did not differ at baseline. At follow-up, those with CP experienced a more modest decrease in symptoms' severity and no improvement in any domain of psychomotor disturbance, contrasting with a decrease of over 40 % from the baseline values of CORE in patients without CP (non-CP). Initial and final scores were respectively: HAM-D CP 24.06 and 19.3, Δ = -4.75; HAM-D non-CP 22.92 and 14.7, Δ = -8.21; CORE CP 5.36 and 5.24, Δ = -0.12; CORE non-CP 5.8 and 3.22, Δ = -2.57. There was no interaction with TH or life quality. Model adjustments for psychotropic drugs received and sensitivity analysis excluding somatic symptoms from severity scales did not impact the results.

LIMITATIONS

Findings may not replicate in mildly depressed patients from primary care. Pain scales were not applied.

CONCLUSIONS

Individuals with chronic pain showed a suboptimal response to depression treatment, regardless of the medications used or TH levels.

Electroacupuncture promotes synaptic plasticity in rats with chronic inflammatory pain-related depression by upregulating BDNF/TrkB/CREB signaling pathway

BACKGROUND

Chronic inflammatory pain (CIP) frequently coincides with depression among patients. The onset and development of pain and depression are associated with altered neural synaptic plasticity. Electroacupuncture (EA) can effectively relieve CIP and depression. However, the underlying mechanisms have not been fully illustrated.

OBJECTIVE

To explore whether EA can relieve CIP and depression by regulating hippocampal synaptic plasticity, and the present study offers foundational evidence for the efficacy of EA in treating CIP-related depression (CIPD).

METHODS

Rats were divided into four groups: 0.9% normal saline group, complete Freund's adjuvant (CFA) group, CFA + duloxetine group, and CFA + EA group. Pain hypersensitivity was detected by mechanical withdrawal threshold and thermal paw withdrawal latency, and the depression level was gauged using the open field test, the sucrose preference test, and the forced swimming test. The morphology of the hippocampal neurons was observed using Nissl staining. The protein expression levels of synuclein (Syn), postsynaptic density protein-95 (PSD-95), brain-derived neurotrophic factors (BDNFs), tyrosine-protein kinase B (TrKB), p-TrkB, cAMP response element binding protein (CREB), and p-CREB were measured by western blotting and immunofluorescence staining. BDNF and TrkB mRNA expression were detected using quantitative real-time polymerase chain reaction (PCR) (qRT-PCR). The content of 5-hydroxytryptamine (5-HT) and γ-aminobutyric acid (GABA) was detected using enzyme-linked immunosorbent assay, and the glutamic acid (Glu) content was determined using the ultraviolet colorimetry method. The hippocampal neuron ultrastructure was observed using transmission electron microscopy.

RESULTS

EA could alleviate CIP and related depressive behaviors as well as protect the hippocampal neuronal structure from damage and regulate 5-HT/GABA/Glu levels in the hippocampus. Additionally, EA could significantly increase the expression of synapse-associated proteins such as PSD-95 and Syn by activating the BDNF/TrKB/CREB signaling pathway.

CONCLUSION

EA improves pain and depressive behaviors in CIPD rats, and the mechanism may be related to synaptic plasticity mediated by the BDNF/TrKB/CREB signaling pathway.

Effects of low-level laser therapy on burning pain and quality of life in patients with burning mouth syndrome: a systematic review and meta-analysis

BACKGROUND

Burning mouth syndrome (BMS) is a complex chronic pain disorder that significantly impairs patients' quality of life. Low-level laser therapy (LLLT) uses infrared or near-infrared light to produce analgesic, anti-inflammatory, and biological stimulation effects. The aim of this systematic review is to evaluate the effect of LLLT on burning pain, quality of life, and negative emotions in patients with BMS.

METHODS

The PubMed, Embase, Cumulative Index of Nursing and Allied Health Literature (CINAHL), Cochrane Library, Web of Science, and Scopus databases were searched up January 2023 to identify relevant articles. All randomized controlled trials that were published in English and examined the use of LLLT treatment for BMS were included. The methodological quality of the included trials was assessed using the Cochrane risk of bias tool for randomized controlled trials (RCTs). A meta-analysis was performed to evaluate burning pain, quality of life, and negative emotions. Sensitivity, subgroup, and funnel plot analyses were also carried out.

RESULTS

Fourteen RCTs involving a total of 550 patients with BMS met the inclusion criteria. The results showed that LLLT (measured by the Visual Analog Scale; SMD: -0.87, 95% CI: -1.29 to -0.45, P < 0.001) was more effective for reducing burning pain than placebo LLLT or clonazepam. LLLT improved quality of life (evaluated by the Oral Health Impact Profile-14; SMD: 0.01, 95% CI: -0.58 to 0.60, P = 0.97) and negative emotions (evaluated by the Hospital Anxiety and Depression Scale; SMD: -0.12, 95% CI: -0.54 to 0.30, P = 0.59), but these effects were not statistically significant.

CONCLUSIONS

The meta-analysis revealed that LLLT may be an effective therapy for improving burning pain in patients with BMS, and producing a positive influence on quality of life and negative emotions. A long-term course of intervention, a larger sample size, and a multidisciplinary intervention design are urgently needed in future research.

TRIAL REGISTRATION

PROSPERO registration number: CRD42022308770.

Nomogram for stratifying patients with lifelong premature ejaculation before using the PHQ-9: An observational study

OBJECTIVE

A PHQ-9 score ≥ 15, represented as PHQ-9⁺ , indicates major depressive disorder (MDD). On using PHQ-9, the psychological burden of several patients with lifelong premature ejaculation (LPE) gets aggravated, which may lead to LPE development. We aim to construct a nomogram for predicting the individual risk of PHQ-9⁺ in patients with LPE and discerning those with low risks, who should avoid the PHQ-9.

METHODS

The nomogram was constructed by analysing data of 802 patients from Xijing Hospital and Northwest Women's & Children's Hospital. The LASSO and multivariable logistic regressions were used to identify independent predictors of PHQ-9⁺ , used for developing the nomogram. The discrimination, calibration and clinical usefulness of the nomogram were assessed in the derivation cohort and an independent validation cohort, which was composed of 505 prospectively enrolled patients from Daxing Hospital and Xijing Hospital.

RESULTS

The duration of PE, IELT, a history of PE exacerbation, IIEF-5 score, urinary frequency and physical pain score were identified as independent predictors. The nomogram showed excellent calibration, discrimination and clinical usefulness in the derivation and validation cohorts, with a predictive accuracy of 0.781 and 0.763, respectively. Based on this nomogram, patients were divided into not recommended, recommended and strongly recommended PHQ-9 filling groups, with PHQ-9⁺ rates of 3.5%, 9.3% and 30.7%, respectively.

CONCLUSION

A nomogram to discern LPE patients with low risks of PHQ-9⁺ was established. This tool can increase the positivity of MDD screening and may improve the therapeutic outcomes of those in the low-risk group.

Comprehensive Targeted Treatment for Neuropathic and Nociceptive Pain in Palliative Care Patients

BACKGROUND

Pain is a common symptom in patients with advanced, metastatic, or terminal cancer. Neuropathic pain and psycho-emotional suffering are factors that increase the difficulty of pain management. Pain control in patients with cancer remains a challenge for medical professionals.

STUDY QUESTION

What is the evolution of neuropathic/mixed pain compared with nociceptive pain under standardized treatment in patients with cancer?

STUDY DESIGN

A prospective, longitudinal, open-label, nonrandomized study was conducted on patients with cancer pain.

MEASURES AND OUTCOMES

Pain type was assessed at admission using the modified Brief Pain Inventory, and pain intensity was assessed daily using the Numerical Rating Scale for 14 days and on days 21 and 28. Screening of depression was performed on days 1, 7, 14, 21, and 28 using the Hamilton Depression Rating Scale. Patients with pain and depression received analgesics with antidepressants, while patients without depression received analgesics or analgesics with an anticonvulsant depending on the pain subtype.

RESULTS

Of 72 patients, 23 had nociceptive pain and 49 had neuropathic/mixed pain. At admission, pain intensity was higher for patients with neuropathic/mixed pain compared with nociceptive pain (mean values: 7.06 vs. 5.82) with statistical significance (P = 0.001) and remained as such at the end of this study (mean values: 3.77 vs. 2.73). A decrease in the mean pain intensity was observed in all types of pain, but without statistical significance regardless of pain type and treatment protocol used (P = 0.77). If depression was present, antidepressants combined with analgesics decreased pain and depression scores significantly (P = 0.001).

CONCLUSIONS

Patients with neuropathic/mixed pain have higher levels of pain and lower response to treatment. Identifying psycho-emotional suffering can improve pain control by intervening in the physical and psycho-emotional components of pain.

Reciprocal effects between depressive symptoms and pain in veterans over 50

OBJECTIVE

Depression and chronic pain are major problems in American veterans, yet there is limited long-term research examining how they relate to one another in this population. This study examined the relationship between depressive symptoms and pain in U.S. veterans aged 50+.

METHODS

This study used data on veterans from the 2002-2016 waves of the Health and Retirement Study (n = 4,302), a large-scale observational study of Americans aged 50+. Measures included a short form of the Center for Epidemiologic Studies Depression scale and two items assessing the presence and degree of pain. Analyses included random intercept cross-lagged panel models (RI-CLPM).

RESULTS

In the RI-CLPM, there were roughly equivalent cross-lagged effects between depressive symptoms and pain. There was also evidence that depressive symptoms and pain have a trait-like component and that these trait-like characteristics are associated.

CONCLUSIONS

These findings indicate that depressive symptoms and pain in veterans are stable characteristics in American veterans over 50. There appear to be reciprocal effects between the two, whereby deviations in one's typical depressive symptoms predict subsequent deviations in one's pain level and vice-versa; however, the size of these effects is very small. These findings suggest that clinicians should treat both depressive symptoms and pain, rather than assume that treatment benefits in one domain will lead to major benefits in another.

How environmental enrichment balances out neuroinflammation in chronic pain and comorbid depression and anxiety disorders

Depression and anxiety commonly occur in chronic pain states and the coexistence of these diseases worsens outcomes for both disorders and may reduce treatment adherence and response. Despite the advances in the knowledge of chronic pain mechanisms, pharmacological treatment is still unsatisfactory. Research based on exposure to environmental enrichment is currently under investigation and seems to offer a promising low-cost strategy with no side effects. In this review, we discuss the role of inflammation as a major biological substrate and aetiological factor of chronic pain and depression/anxiety and report a collection of preclinical evidence of the effects and mechanisms of environmental enrichment. As microglia participates in the development of both conditions, we also discuss microglia as a potential target underlying the beneficial actions of environmental enrichment in chronic pain and comorbid depression/anxiety. We also discuss how alternative interventions under clinical guidelines, such as environmental enrichment, may improve treatment compliance and patient outcomes.